title: A novel GCAP1(N104K) mutation in EF-hand 3 (EF3) linked to autosomal dominant cone dystrophy.
abstract: The GUCA1A gene encodes a guanylate cyclase activating protein (GCAP1) that is involved in regulation of phototransduction in the vertebrate retina. We discovered a novel C312A transversion in exon 2 of the human GUCA1A gene, replacing Asn-104 (N104) in GCAP1 with Lys (K), in two affected members of a family with dominant cone dystrophy. The mutation N104K is located in the third EF-hand motif (EF3) shown previously to be instrumental in converting Ca2+-free GCAP1 to a GC inhibitor in the Ca2+-bound form. In one patient, rod ERGs were fairly stable over a 12-year-period whereas 30 Hz flicker ERG and single-flash cone ERGs declined. In both patients, double-flash ERGs showed that rod recovery from an intense test flash was significantly delayed. The EC(50) for GC stimulation shifted from approximately 250 nM in wild-type GCAP1 to approximately 800 nM in the GCAP1(N104K) mutant suggesting inability of the mutant to assume an inactive form under physiological conditions. The replacement of N104 by K in GCAP1 is the first naturally occurring mutation identified in the EF3 loop. The rod recovery delays observed in double-flash ERG of affected patients suggest a novel dominant-negative effect that slows GC stimulation.
authors.affiliation: Department of Biology, University of Utah, Salt Lake City, UT 84132, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Jiang
authors.forename: Dianna
authors.initials: D
authors.lastname: Wheaton
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Bereta
authors.forename: Kang
authors.initials: K
authors.lastname: Zhang
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Palczewski
authors.forename: David G
authors.initials: DG
authors.lastname: Birch
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Baehr
mesh_terms: D000328:Adult; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism; D004252:DNA Mutational Analysis / Q000379:methods; D004596:Electroretinography / Q000379:methods; D004789:Enzyme Activation; D006162:Guanylate Cyclase / Q000378:metabolism; D051604:Guanylate Cyclase-Activating Proteins / Q000235:genetics* / Q000494:pharmacology; D006801:Humans; D055537:Light Signal Transduction / Q000235:genetics; D008297:Male; D008875:Middle Aged; D015394:Molecular Structure; D009154:Mutation; D010375:Pedigree; D011956:Receptors, Cell Surface / Q000378:metabolism; D012162:Retinal Degeneration / Q000235:genetics*
chemical_list: C496736:GUCA1A protein, human; D051604:Guanylate Cyclase-Activating Proteins; D011956:Receptors, Cell Surface; C110715:guanylate cyclase 1; D006162:Guanylate Cyclase; D002118:Calcium