SMS1, a high-copy suppressor of the yeast mas6 mutant, encodes an essential inner membrane protein required for mitochondrial protein import

KR Ryan, MM Menold, S Garrett and RE Jensen

Department of Cell Biology and Anatomy, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.

MAS6 encodes an essential inner membrane protein required for mitochondrial protein import in the yeast Saccharomyces cerevisiae (Emtage and Jensen, 1993). To identify new inner membrane import components, we isolated a high-copy suppressor (SMS1) of the mas6-1 mutant. SMS1 encodes a 16.5-kDa protein that contains several potential membrane-spanning domains. The Sms1 protein is homologous to the carboxyl-terminal domain of the Mas6 protein. Like Mas6p, Sms1p is located in the mitochondrial inner membrane and is an essential protein. Depletion of Sms1p from cells causes defects in the import of several mitochondrial precursor proteins, suggesting that Sms1p is a new inner membrane import component. Our observations raise the possibility that Sms1p and Mas6p act together to translocate proteins across the inner membrane.

Volume 5, Issue 5, pp. 529-538, 05/01/1994
Copyright © 1994 by The American Society for Cell Biology

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