MSS1, a nuclear-encoded mitochondrial GTPase involved in the expression of COX1 subunit of cytochrome c oxidase.

Mutations in the MSS1 gene render the yeast cells respiratory deficient only in the presence of the PR454 mutation (paromomycin resistance) in the mitochondrial 15 S ribosomal RNA gene. The MSS1 gene product works in association with the small subunit of mitoribosomes and seems to play some part in mitochondrial translation. The block in the splicing of introns of cytochrome c oxidase subunit 1 could result from a specific impeding of the translation of maturases. Comparison of the MSS1 putative protein with data libraries revealed that it contains, in its second half, the consensus sequences characteristic of GTP binding proteins and is very homologous to the bacterial "genes 50K".