Cloning and characterization of a G protein α-subunit-encoding gene from the basidiomycete, Coprinus congregatus

Abstract

Complementary DNA (cDNA) clones encoding two G protein α-subunit proteins (CGPα1 and CGPα2) were isolated from a Coprinus congregatus (Cc) hyphal tip cell (HTC) library using PCR-generated biotinylated G protein probes. Sequence analysis of the Cc cgpαl gene indicates that the gene contains an open reading frame (ORF) that translates into a putative 353-amino-acid (aa) product. The predicted CGPαl protein exhibits similarity to all known G protein α-subunits (it has all of the consensus regions for a GTP-binding protein), especially the mammalian retinal G protein, transducin. The CGPαl aa sequence is 50% identical overall to the transducin subfamily, cgpαl shares the same aa size grouping as transducin α-subunits and, unlike many other G proteins, both CGPαl and transducin seem to possess a cholera toxin (CTX)- and pertussis toxin (PTX)-sensitive site. Preliminary reverse transcription PCR (RT-PCR) analysis of cgpαl and cgpα2 mRNA expression revealed that, unlike cgpα2 which seems to be constitutively expressed, cgpαl is expressed only in HTC that are competent in responding to light. Thus, the cgpαl product, CGPαl, is a likely candidate for regulating the blue light-induced signal transduction photomorphogenesis system found in Cc