title: The cone-specific calcium sensor guanylate cyclase activating protein 4 from the zebrafish retina.
abstract: Guanylate cyclase activating proteins (GCAPs) serve as neuronal Ca(2+)-sensor proteins in vertebrate rod and cone photoreceptor cells. Zebrafish express in their retina a variety of six different GCAPs, of which four are specific for cone cells. One isoform, zGCAP4, is mainly expressed in double cones and long single cones. We cloned the zGCAP4 gene, purified non-myristoylated and myristoylated forms of the protein after heterologous expression in Escherichia coli and studied its properties: zGCAP4 was a strong activator of membrane-bound guanylate cyclases from bovine and zebrafish retina, showing half-maximal activation at 520-570 nM free Ca(2+) concentration. Furthermore, the Ca(2+)-sensitive activation properties of non-myristoylated and myristoylated zGCAP4 were similar, indicating no influence of the myristoyl moiety on Ca(2+)-sensor function. Myristoylated zGCAP4 showed low affinity for membranes and did not exhibit a Ca(2+)-myristoyl switch, a feature typical of some but not all neuronal Ca(2+)-sensor proteins. However, tryptophan fluorescence studies and Ca(2+)-dependent differences in protease accessibility revealed Ca(2+)-induced conformational changes in myristoylated and non-myristoylated zGCAP4, indicating the operation as a Ca(2+) sensor. Thus, expression and biochemical properties of zGCAP4 are in agreement with its function as an efficient Ca(2+)-sensitive regulator of guanylate cyclase activity in cone vision.
authors.affiliation: Biochemistry Group, Institute of Biology and Environmental Science, Faculty V, Carl von Ossietzky University Oldenburg, 26111, Oldenburg, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Behnen
authors.forename: Alexander
authors.initials: A
authors.lastname: Scholten
authors.forename: Nina
authors.initials: N
authors.lastname: Rätscho
authors.forename: Karl-Wilhelm
authors.initials: KW
authors.lastname: Koch
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000032:analysis / Q000378:metabolism*; D020013:Calcium Signaling; D005786:Gene Expression Regulation / Q000235:genetics; D051604:Guanylate Cyclase-Activating Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D057927:Hydrophobic and Hydrophilic Interactions; D008969:Molecular Sequence Data; D012160:Retina / Q000378:metabolism*; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D051604:Guanylate Cyclase-Activating Proteins; D029961:Zebrafish Proteins; D002118:Calcium
references.citation: Annu Rev Biochem. 1988;57:69-99
references.pmid: 3052287
references.citation: J Neurobiol. 2003 Jan;54(1):148-60
references.pmid: 12486702
references.citation: J Biol Chem. 1995 Oct 20;270(42):25200-6
references.pmid: 7559656
references.citation: J Mol Biol. 1982 May 5;157(1):105-32
references.pmid: 7108955
references.citation: J Neurosci. 2003 Jan 15;23(2):470-80
references.pmid: 12533607
references.citation: J Mol Evol. 2004 Aug;59(2):204-217
references.pmid: 15486694
references.citation: J Neurochem. 2007 Nov;103(4):1439-46
references.pmid: 17868328
references.citation: J Exp Biol. 2005 Apr;208(Pt 7):1337-45
references.pmid: 15781894
references.citation: Physiol Rev. 2001 Jan;81(1):117-151
references.pmid: 11152756
references.citation: Neuron. 1994 Aug;13(2):395-404
references.pmid: 7520254
references.citation: J Biol Chem. 2006 Aug 18;281(33):23830-41
references.pmid: 16793776
references.citation: J Biol Chem. 1999 Jul 2;274(27):19329-37
references.pmid: 10383444
references.citation: J Biol Chem. 1999 Mar 5;274(10):6526-35
references.pmid: 10037746
references.citation: J Comp Neurol. 1984 Mar 20;224(1):107-15
references.pmid: 6715574
references.citation: Eur J Biochem. 2003 Sep;270(18):3814-21
references.pmid: 12950265
references.citation: Nat Rev Neurosci. 2007 Mar;8(3):182-93
references.pmid: 17311005
references.citation: Anal Biochem. 1976 May 7;72:248-54
references.pmid: 942051
references.citation: Int J Dev Neurosci. 2001 Nov;19(7):621-9
references.pmid: 11705666
references.citation: J Biol Chem. 2002 Apr 19;277(16):14227-37
references.pmid: 11836243
references.citation: Proc Natl Acad Sci U S A. 1992 Dec 1;89(23):11569-73
references.pmid: 1454850
references.citation: Methods Enzymol. 2000;316:536-57
references.pmid: 10800700
references.citation: Neuron. 1996 Aug;17(2):323-31
references.pmid: 8780655
references.citation: Biochemistry. 2002 Oct 29;41(43):13021-8
references.pmid: 12390029
references.citation: Vis Neurosci. 2004 Jul-Aug;21(4):599-609
references.pmid: 15579223
references.citation: J Physiol. 2001 Apr 15;532(Pt 2):305-21
references.pmid: 11306652
references.citation: J Biol Chem. 1996 Apr 5;271(14):8022-7
references.pmid: 8626484
references.citation: Eur J Biochem. 2004 Sep;271(18):3785-93
references.pmid: 15355355
references.citation: J Physiol. 2002 Aug 1;542(Pt 3):829-41
references.pmid: 12154182
references.citation: Genetics. 2003 Feb;163(2):663-75
references.pmid: 12618404
references.citation: Eur J Neurosci. 2002 Jan;15(1):63-78
references.pmid: 11860507
references.citation: Biochim Biophys Acta. 2002 Nov 4;1600(1-2):111-7
references.pmid: 12445466
references.citation: J Physiol. 2002 Aug 1;542(Pt 3):843-54
references.pmid: 12154183
references.citation: J Gen Physiol. 1999 Feb;113(2):267-77
references.pmid: 9925824