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Specific molecular alterations in the norpA ‐encoded phospholipase C of Drosophila and their effects on electrophysiological responses in vivo
Author(s) -
Yoon Jaeseung,
Leung HungTat,
Lee Seunghee,
Geng Chaoxian,
Kim Younkyung,
Baek Kwanghee,
Pak William L.
Publication year - 2004
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2004.02384.x
Subject(s) - mutant , visual phototransduction , phospholipase c , biology , phospholipase , mutation , erg , biochemistry , microbiology and biotechnology , gene , signal transduction , retinal , enzyme
A large number of mutants in the norpA gene, which encodes the phospholipase C (PLC) involved in Drosophila phototransduction, is available for the investigation of the effects of specific amino acid substitutions in PLC on biochemical and electrophysiological properties of these mutants. Of the 47 norpA mutants screened for PLC protein content, all but one ( H43 ) displayed drastically decreased amounts of the protein suggesting that almost any mutational alteration has a deleterious effect on the integrity of the protein. Three new amino acids were identified in the catalytic domains X and Y that are important for PLC catalytic activity and the generation of photoreceptor responses (ERG). One of them was found substituted in H43 , which showed a low specific PLC activity, a pronounced decrease in ERG sensitivity, and a wild‐type‐like response termination time. The response termination times obtained from three mutants was found to be approximately inversely proportional to the amount of PLC. In addition, we show that (i) the specific PLC activity is a key factor determining the photoreceptor sensitivity; (ii) the catalytic activity and response termination are separable functions of PLC; and (iii) a mutation in the putative Gα‐interacting C2 domain causes a preferentially strong defect in latency.