Yarrowia lipolytica SRP receptor alpha-subunit

The Yarrowia lipolytica SRP101 homologue encoding the signal recognition particle (SRP) receptor alpha-subunit (SRalphap) was cloned using degenerate primers designed for conserved GTP-binding domains. Sequencing of 2814 nucleotides revealed an open reading frame of 1671 base pairs encoding a putative protein of 557 amino acids with a predicted molecular mass of 61 kDa. Like other SRP101 homologues, Y. lipolytica SRP101 contains a highly conserved C-terminal GTP binding site. It has 44%, 34% and 22% sequence identity with S. cerevisiae, mammalian and Escherichia coli homologues, respectively. As found for SRP protein subunits of Y. lipolytica, SRP101 is important but not essential for cell growth. A conditional mutation in SRP101 affected synthesis/translocation of alkaline extracellular protease and Kar2p consistent with Srp101p functioning as an SRP receptor subunit. The SRP101 sequence has been deposited in GenBank under Accession No. AF132597.