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Autoinhibitory regulation of soluble adenylyl cyclase
Author(s) -
Chaloupka James A.,
Bullock Stewart A.,
Iourgenko Vadim,
Levin Lonny R.,
Buck Jochen
Publication year - 2006
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.20409
Subject(s) - adenylyl cyclase , biology , gene isoform , adcy9 , recombinant dna , enzyme , adcy10 , biochemistry , microbiology and biotechnology , gene
Soluble adenylyl cyclase is an evolutionarily conserved bicarbonate sensor that plays a crucial role in cAMP dependent processes that occur during mammalian fertilization. sAC protein is expressed at the highest levels in male germ cells, and is found to occur as one of two known isoforms: a truncated protein (sAC t ) that consists almost exclusively of the two conserved catalytic domains (C1 and C2), and a full‐length form (sAC fl ) that contains an additional noncatalytic C‐terminal region. Several studies suggested sAC t was more active than sAC fl . We now demonstrate that the specific activity of sAC t is at least 10‐fold higher than the specific activity of sAC fl . Using deletion analysis and a novel genetic screen to identify activating mutations, we uncovered an autoinhibitory region just C‐terminal to the C2 domain. Kinetic analysis of purified recombinant sAC revealed this autoinhibitory domain functions to lower the enzyme's V max without altering its affinity for substrate or regulation by any of the known modulators of sAC activity. Our results identify an additional regulatory mechanism specific to the sAC fl isoform. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.