SHY1, the Yeast Homolog of the MammalianSURF-1 Gene, Encodes a Mitochondrial Protein Required for Respiration

Abstract

C173 and W125 are pet mutants of Saccharomyces cerevisiae, partially deficient in cytochrome oxidase but with elevated concentrations of cytochrome c. Assays of electron transport chain enzymes indicate that the mutations exert different effects on the terminal respiratory pathway, including an inefficient transfer of electrons between the bc 1 and the cytochrome oxidase complexes. A cloned gene capable of restoring respiration in C173/U1 and W125 is identical to reading frame YGR112w of yeast chromosome VII (GenBank Z72897). The encoded protein is homologous to the product of the mammalian SURF-1 gene. In view of the homology, the yeast gene has been designated SHY1 (Surf Homolog of Yeast). An antibody against the carboxyl-terminal half of Shy1p has been used to localize the protein in the inner mitochondrial membrane. Deletion of part of SHY1 produces a phenotype similar to that of G91 mutants. Disruption of SHY1 at a BamHI site, located approximately 2/3 of the way into the gene, has no obvious phenotypic consequence. This evidence, together with the ability of a carboxyl-terminal coding sequence starting from the BamHI site to complement a shy1 mutant, suggests that the Shy1p contains two domains that can be separately expressed to form a functional protein.

Two Distinct and Independent Mitochondrial Targeting Signals Function in the Sorting of an Inner Membrane Protein, Cytochromec 1

“…Interestingly, Shy1p which spans the inner membrane twice appears to be divided into two functional domains. Both domains can be separately expressed to form a functional protein (34). This finding implies that both of these domains contain their own independent mitochondrial targeting and submitochondrial sorting signals.…”

“…They contain potential internal mitochondrial targeting signals COOH-terminal to their second transmembrane segment, in addition to their NH 2 -terminal presequences. These proteins include, for example, Yta10p (Afg3p), Yta12p (Rca1p) (30 -33), and the recently described Shy1p protein (34). Interestingly, Shy1p which spans the inner membrane twice appears to be divided into two functional domains.…”

Regulation of the heme A biosynthetic pathway in Saccharomyces cerevisiae

“…(not shown) mutants that retain 10^25% heme A. The heme A is probably associated with the residual COX present in these strains [25,26]. Since COX de¢cient mutants have low ( 6 10%) concentrations of Cox1p, the heme-bearing component of the enzyme, the decrease in heme A could be due to turnover of heme A not bound to Cox1p.…”

MTO1 Codes for a Mitochondrial Protein Required for Respiration in Paromomycin-resistant Mutants of Saccharomyces cerevisiae

“…Mitochondria were assayed for NADH-cytochrome c reductase, succinate-cytochrome-c reductase, and cytochrome oxidase as described previously (13) Construction of W303⌬MTO1 and W303⌬MSS1-A null allele of MTO1 was constructed by polymerase chain reaction amplification of the 5Ј and 3Ј sequences adjacent to the gene using the divergent primers 5Ј-gccgggtaccgtatgtaaccatcaaattcg and 5Ј-cgccggtaccgttctttggggcgtttagc. The template for the amplification consisted of the 3.5-kb BamHISacI fragment cloned in pUC18.…”