Adenylate cyclase(EC 4.6.1.1, also commonly known asadenyl cyclaseandadenylyl cyclase,abbreviatedAC) is anenzymewith systematic nameATP diphosphate-lyase (cyclizing; 3′,5′-cyclic-AMP-forming).It catalyzes the following reaction:
| Adenylate cyclase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 Adenylate cyclase (calmodulin sensitive)trimer,Bacillus anthracis Epinephrinebinds its receptor, that associates with aheterotrimericG protein. TheG proteinassociates with adenylyl cyclase, which convertsATPtocAMP,spreading the signal.[1] | |||||||||
| Identifiers | |||||||||
| EC no. | 4.6.1.1 | ||||||||
| CAS no. | 9012-42-4 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDBstructures | RCSB PDBPDBePDBsum | ||||||||
| Gene Ontology | AmiGO/QuickGO | ||||||||
| |||||||||
- ATP = 3′,5′-cyclic AMP + diphosphate
It has key regulatory roles in essentially allcells.[2]It is the mostpolyphyleticknownenzyme:six distinct classes have been described, allcatalyzingthe same reaction but representing unrelatedgenefamilieswith no knownsequence or structural homology.[3]The best known class of adenylyl cyclases is class III or AC-III (Roman numerals are used for classes). AC-III occurs widely ineukaryotesand has important roles in many humantissues.[4]
All classes of adenylyl cyclasecatalysethe conversion ofadenosine triphosphate(ATP) to3',5'-cyclic AMP(cAMP) andpyrophosphate.[4]Magnesiumionsare generally required and appear to be closely involved in the enzymatic mechanism. The cAMP produced by AC then serves as a regulatory signal via specific cAMP-bindingproteins,eithertranscription factors,enzymes (e.g., cAMP-dependentkinases), or iontransporters.
Classes
editClass I
edit| Adenylate cyclase, class-I | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | Adenylate_cycl | ||||||||
| Pfam | PF01295 | ||||||||
| InterPro | IPR000274 | ||||||||
| PROSITE | PDOC00837 | ||||||||
| |||||||||
The first class of adenylyl cyclases occur in many bacteria includingE. coli(as CyaAP00936[unrelated to the Class II enzyme]).[4]This was the first class of AC to be characterized. It was observed thatE. colideprived of glucose produce cAMP that serves as an internal signal to activate expression of genes for importing and metabolizing other sugars. cAMP exerts this effect by binding the transcription factorCRP,also known as CAP. Class I AC's are large cytosolic enzymes (~100 kDa) with a large regulatory domain (~50 kDa) that indirectly senses glucose levels. As of 2012[update],no crystal structure is available for class I AC.
Some indirect structural information is available for this class. It is known that the N-terminal half is the catalytic portion, and that it requires two Mg2+ions. S103, S113, D114, D116 and W118 are the five absolutely essential residues. The class I catalytic domain (PfamPF12633) belongs to the same superfamily (PfamCL0260) as the palm domain ofDNA polymerase beta(PfamPF18765). Aligning its sequence onto the structure onto a related archaealCCA tRNA nucleotidyltransferase(PDB:1R89) allows for assignment of the residues to specific functions:γ-phosphatebinding, structural stabilization, DxD motif for metal ion binding, and finally ribose binding.[5]
Class II
editThese adenylyl cyclases are toxins secreted by pathogenic bacteria such asBacillus anthracis,Bordetella pertussis,Pseudomonas aeruginosa,andVibrio vulnificusduring infections.[6]These bacteria also secrete proteins that enable the AC-II to enter host cells, where the exogenous AC activity undermines normal cellular processes. The genes for Class II ACs are known ascyaA,one of which isanthrax toxin.Several crystal structures are known for AC-II enzymes.[7][8][9]
Class III
edit| Adenylyl cyclase class-3/guanylyl cyclase | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | Guanylate_cyc | ||||||||
| Pfam | PF00211 | ||||||||
| Pfamclan | CL0276 | ||||||||
| InterPro | IPR001054 | ||||||||
| SMART | SM00044 | ||||||||
| PROSITE | PS50125 | ||||||||
| SCOP2 | 1tl7/SCOPe/SUPFAM | ||||||||
| TCDB | 8.A.85 | ||||||||
| OPM superfamily | 546 | ||||||||
| OPM protein | 6r3q | ||||||||
| |||||||||
These adenylyl cyclases are the most familiar based on extensive study due to their important roles in human health. They are also found in some bacteria, notablyMycobacterium tuberculosiswhere they appear to have a key role in pathogenesis. Most AC-III's are integral membrane proteins involved in transducing extracellular signals into intracellular responses. A Nobel Prize was awarded toEarl Sutherlandin 1971 for discovering the key role of AC-III in human liver, where adrenaline indirectly stimulates AC to mobilize stored energy in the "fight or flight" response. The effect of adrenaline is via aG proteinsignaling cascade, which transmits chemical signals from outside the cell across the membrane to the inside of the cell (cytoplasm). The outside signal (in this case, adrenaline) binds to a receptor, which transmits a signal to the G protein, which transmits a signal to adenylyl cyclase, which transmits a signal by convertingadenosine triphosphatetocyclic adenosine monophosphate(cAMP). cAMP is known as asecond messenger.[10]
Cyclic AMPis an important molecule ineukaryoticsignal transduction,a so-calledsecond messenger.Adenylyl cyclases are often activated or inhibited byG proteins,which are coupled to membrane receptors and thus can respond to hormonal or other stimuli.[11]Following activation of adenylyl cyclase, the resulting cAMP acts as a second messenger by interacting with and regulating other proteins such asprotein kinase Aandcyclic nucleotide-gated ion channels.[11]
Photoactivated adenylyl cyclase(PAC) was discovered inEuglena gracilisand can be expressed in other organisms through genetic manipulation. Shining blue light on a cell containing PAC activates it and abruptly increases the rate of conversion of ATP to cAMP. This is a useful technique for researchers in neuroscience because it allows them to quickly increase the intracellular cAMP levels in particular neurons, and to study the effect of that increase in neural activity on the behavior of the organism.[12]A green-light activated rhodopsin adenylyl cyclase (CaRhAC) has recently been engineered by modifying the nucleotide binding pocket of rhodopsinguanylyl cyclase.
Structure
edit
Most class III adenylyl cyclases are transmembraneproteinswith 12 transmembrane segments. The protein is organized with 6 transmembrane segments, then the C1 cytoplasmic domain, then another 6 membrane segments, and then a second cytoplasmic domain called C2. The important parts for function are the N-terminus and the C1 and C2 regions. The C1a and C2a subdomains are homologous and form an intramolecular 'dimer' that forms the active site. InMycobacterium tuberculosisand many other bacterial cases, the AC-III polypeptide is only half as long, comprising one 6-transmembrane domain followed by a cytoplasmic domain, but two of these form a functional homodimer that resembles the mammalian architecture with two active sites. In non-animal class III ACs, the catalytic cytoplasmic domain is seen associated with other (not necessarily transmembrane) domains.[13]
Class III adenylyl cyclase domains can be further divided into four subfamilies, termed class IIIa through IIId. Animal membrane-bound ACs belong to class IIIa.[13]: 1087
Mechanism
editThe reaction happens with two metal cofactors (Mg or Mn) coordinated to the two aspartate residues on C1. They perform a nucleophilic attack of the 3'-OH group of the ribose on the α-phosphoryl group of ATP. The two lysine and aspartate residues on C2 selects ATP over GTP for the substrate, so that the enzyme is not a guanylyl cyclase. A pair of arginine and asparagine residues on C2 stabilizes the transition state. In many proteins, these residues are nevertheless mutated while retaining the adenylyl cyclase activity.[13]
Types
editThere are ten known isoforms of adenylyl cyclases inmammals:
These are also sometimes called simply AC1, AC2, etc., and, somewhat confusingly, sometimes Roman numerals are used for these isoforms that all belong to the overall AC class III. They differ mainly in how they are regulated, and are differentially expressed in various tissues throughout mammalian development.
Regulation
editAdenylyl cyclase is regulated by G proteins, which can be found in the monomeric form or the heterotrimeric form, consisting of three subunits.[2][3][4]Adenylyl cyclase activity is controlled by heterotrimeric G proteins.[2][3][4]The inactive or inhibitory form exists when the complex consists of alpha, beta, and gamma subunits, with GDP bound to the alpha subunit.[2][4]In order to become active, a ligand must bind to the receptor and cause a conformational change.[2]This conformational change causes the alpha subunit to dissociate from the complex and become bound to GTP.[2]This G-alpha-GTP complex then binds to adenylyl cyclase and causes activation and the release of cAMP.[2]Since a good signal requires the help of enzymes, which turn on and off signals quickly, there must also be a mechanism in which adenylyl cyclase deactivates and inhibits cAMP.[2]The deactivation of the active G-alpha-GTP complex is accomplished rapidly by GTP hydrolysis due to the reaction being catalyzed by the intrinsic enzymatic activity of GTPase located in the alpha subunit.[2]It is also regulated byforskolin,[11]as well as other isoform-specific effectors:
- Isoforms I, III, and VIII are also stimulated byCa2+/calmodulin.[11]
- Isoforms V and VI are inhibited by Ca2+in a calmodulin-independent manner.[11]
- Isoforms II, IV and IX are stimulated by alpha subunit of the G protein.[11]
- Isoforms I, V and VI are most clearly inhibited by Gi, while other isoforms show less dual regulation by the inhibitory G protein.[11]
- Soluble AC(sAC) is not a transmembrane form and is not regulated by G proteins or forskolin, instead acts as a bicarbonate/pH sensor. It is anchored at various locations within the cell and, withphosphodiesterases,forms local cAMP signalling domains.[14]
Inneurons,calcium-sensitive adenylyl cyclases are located next to calciumion channelsfor faster reaction to Ca2+influx; they are suspected of playing an important role in learning processes. This is supported by the fact that adenylyl cyclases arecoincidence detectors,meaning that they are activated only by several different signals occurring together.[15]In peripheral cells and tissues adenylyl cyclases appear to form molecular complexes with specific receptors and other signaling proteins in an isoform-specific manner.
Function
editIndividual transmembrane adenylyl cyclase isoforms have been linked to numerous physiological functions.[16]Soluble adenylyl cyclase (sAC, AC10) has a critical role in sperm motility.[17]Adenylyl cyclase has been implicated in memory formation, functioning as acoincidence detector.[11][15][18][19][20]
Class IV
edit
| Adenylyl cyclase CyaB | |
|---|---|
| Identifiers | |
| Symbol | CyaB |
| InterPro | IPR008173 |
| CATH | 1YEM |
| SCOP2 | 2ACA/SCOPe/SUPFAM |
| CDD | cd07890 |
AC-IV was first reported in the bacteriumAeromonas hydrophila,and the structure of the AC-IV fromYersinia pestishas been reported. These are the smallest of the AC enzyme classes; the AC-IV (CyaB) fromYersiniais a dimer of 19 kDa subunits with no known regulatory components (PDB:2FJT).[21]AC-IV forms a superfamily with mammalianthiamine-triphosphatasecalled CYTH (CyaB, thiamine triphosphatase).[22]
Classes V and VI
edit| AC Class VI (DUF3095) | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Identifiers | |||||||||
| Symbol | DUF3095 | ||||||||
| Pfam | PF11294 | ||||||||
| InterPro | IPR021445 | ||||||||
| |||||||||
| contact prediction | |||||||||
These forms of AC have been reported in specific bacteria (PrevotellaruminicolaO68902andRhizobiumetliQ8KY20,respectively) and have not been extensively characterized.[23]There are a few extra members (~400 in Pfam) known to be in class VI. Class VI enzymes possess a catalytic core similar to the one in Class III.[24]
Additional images
edit
References
edit- ^"PDB101: Molecule of the Month: G Proteins".RCSB: PDB-101.Retrieved24 August2020.
- ^abcdefghiHancock, John (2010).Cell Signaling.pp. 189–195.
- ^abcSadana R, Dessauer CW (February 2009)."Physiological roles for G protein-regulated adenylyl cyclase isoforms: insights from knockout and overexpression studies".Neuro-Signals.17(1): 5–22.doi:10.1159/000166277.PMC2790773.PMID18948702.
- ^abcdefZhang G, Liu Y, Ruoho AE, Hurley JH (March 1997). "Structure of the adenylyl cyclase catalytic core".Nature.386(6622): 247–253.Bibcode:1997Natur.386..247Z.doi:10.1038/386247a0.PMID9069282.S2CID4329051.
- ^Linder JU (November 2008). "Structure-function relationships in Escherichia coli adenylate cyclase".The Biochemical Journal.415(3): 449–454.doi:10.1042/BJ20080350.PMID18620542.(alignment)
- ^Ahuja N,Kumar P, Bhatnagar R (2004). "The adenylate cyclase toxins".Critical Reviews in Microbiology.30(3): 187–196.doi:10.1080/10408410490468795.PMID15490970.S2CID23893594.
- ^Khanppnavar B, Datta S (September 2018). "Crystal structure and substrate specificity of ExoY, a unique T3SS mediated secreted nucleotidyl cyclase toxin from Pseudomonas aeruginosa".Biochimica et Biophysica Acta (BBA) - General Subjects.1862(9): 2090–2103.doi:10.1016/j.bbagen.2018.05.021.PMID29859257.S2CID44151852.
- ^Guo Q, Shen Y, Lee YS, Gibbs CS, Mrksich M, Tang WJ (September 2005)."Structural basis for the interaction of Bordetella pertussis adenylyl cyclase toxin with calmodulin".The EMBO Journal.24(18): 3190–3201.doi:10.1038/sj.emboj.7600800.PMC1224690.PMID16138079.
- ^Drum CL, Yan SZ, Bard J, Shen YQ, Lu D, Soelaiman S, et al. (January 2002). "Structural basis for the activation of anthrax adenylyl cyclase exotoxin by calmodulin".Nature.415(6870): 396–402.Bibcode:2002Natur.415..396D.doi:10.1038/415396a.PMID11807546.S2CID773562.
- ^Reece J, Campbell N (2002).Biology.San Francisco: Benjamin Cummings. pp.207.ISBN978-0-8053-6624-2.
- ^abcdefghHanoune J, Defer N (April 2001). "Regulation and role of adenylyl cyclase isoforms".Annual Review of Pharmacology and Toxicology.41(1): 145–174.doi:10.1146/annurev.pharmtox.41.1.145.PMID11264454.
- ^Schröder-Lang S, Schwärzel M, Seifert R, Strünker T, Kateriya S, Looser J, et al. (January 2007)."Fast manipulation of cellular cAMP level by light in vivo".Nature Methods.4(1): 39–42.doi:10.1038/nmeth975.PMID17128267.S2CID10616442.
- ^abcLinder JU, Schultz JE (December 2003). "The class III adenylyl cyclases: multi-purpose signalling modules".Cellular Signalling.15(12): 1081–1089.doi:10.1016/s0898-6568(03)00130-x.PMID14575863.
- ^Rahman N, Buck J, Levin LR (November 2013)."pH sensing via bicarbonate-regulated" soluble "adenylyl cyclase (sAC)".Frontiers in Physiology.4:343.doi:10.3389/fphys.2013.00343.PMC3838963.PMID24324443.
- ^abHogan DA, Muhlschlegel FA (December 2011). "Candida albicans developmental regulation: adenylyl cyclase as a coincidence detector of parallel signals".Current Opinion in Microbiology.14(6): 682–686.doi:10.1016/j.mib.2011.09.014.PMID22014725.
- ^Ostrom KF, LaVigne JE, Brust TF, Seifert R, Dessauer CW, Watts VJ, Ostrom RS (April 2022)."Physiological roles of mammalian transmembrane adenylyl cyclase isoforms".Physiological Reviews.102(2): 815–857.doi:10.1152/physrev.00013.2021.PMC8759965.PMID34698552.
- ^Esposito G, Jaiswal BS, Xie F, Krajnc-Franken MA, Robben TJ, Strik AM, et al. (March 2004)."Mice deficient for soluble adenylyl cyclase are infertile because of a severe sperm-motility defect".Proceedings of the National Academy of Sciences of the United States of America.101(9): 2993–2998.Bibcode:2004PNAS..101.2993E.doi:10.1073/pnas.0400050101.PMC365733.PMID14976244.
- ^Willoughby D, Cooper DM (July 2007). "Organization and Ca2+ regulation of adenylyl cyclases in cAMP microdomains".Physiological Reviews.87(3): 965–1010.CiteSeerX10.1.1.336.3746.doi:10.1152/physrev.00049.2006.PMID17615394.
- ^Mons N, Guillou JL, Jaffard R (April 1999)."The role of Ca2+/calmodulin-stimulable adenylyl cyclases as molecular coincidence detectors in memory formation".Cellular and Molecular Life Sciences.55(4): 525–533.doi:10.1007/s000180050311.PMC11147090.PMID10357223.S2CID10849274.
- ^Neve KA, Seamans JK, Trantham-Davidson H (August 2004). "Dopamine receptor signaling".Journal of Receptor and Signal Transduction Research.24(3): 165–205.CiteSeerX10.1.1.465.5011.doi:10.1081/RRS-200029981.PMID15521361.S2CID12407397.
- ^Gallagher DT, Smith NN, Kim SK, Heroux A, Robinson H, Reddy PT (September 2006). "Structure of the class IV adenylyl cyclase reveals a novel fold".Journal of Molecular Biology.362(1): 114–122.doi:10.1016/j.jmb.2006.07.008.PMID16905149.
- ^Kohn G, Delvaux D, Lakaye B, Servais AC, Scholer G, Fillet M, et al. (2012)."High inorganic triphosphatase activities in bacteria and mammalian cells: identification of the enzymes involved".PLOS ONE.7(9): e43879.Bibcode:2012PLoSO...743879K.doi:10.1371/journal.pone.0043879.PMC3440374.PMID22984449.
- ^Cotta MA, Whitehead TR, Wheeler MB (July 1998)."Identification of a novel adenylate cyclase in the ruminal anaerobe, Prevotella ruminicola D31d".FEMS Microbiology Letters.164(2): 257–260.doi:10.1111/j.1574-6968.1998.tb13095.x.PMID9682474.GenBankAF056932.
- ^Téllez-Sosa J, Soberón N, Vega-Segura A, Torres-Márquez ME, Cevallos MA (July 2002)."The Rhizobium etli cyaC product: characterization of a novel adenylate cyclase class".Journal of Bacteriology.184(13): 3560–3568.doi:10.1128/jb.184.13.3560-3568.2002.PMC135151.PMID12057950.GenBankAF299113.
Further reading
edit- Sodeman W, Sodeman T (2005). "Physiologic- and Adenylate Cyclase-Coupled Beta-Adrenergic Receptors".Sodeman's Pathologic Physiology: Mechanisms of Disease.W B Saunders Co. pp. 143–145.ISBN978-0721610108.
External links
edit
- Adenylyl Cyclasesat the U.S. National Library of MedicineMedical Subject Headings(MeSH)
- Interactive 3D views of Adenylate cyclase atProteopediaAdenylyl_cyclase
