SHM1: a multicopy suppressor of a temperature-sensitive null mutation in the HMG1-like abf2 gene.

HM, an HMG1-like mitochondrial DNA-binding protein, is required for maintenance of the yeast mitochondrial genome when cells are grown in glucose. To better understand the role of HM in mitochondria, we have isolated several multicopy suppressors of the temperature-sensitive defect associated with an abf2 null mutation (lacking HM protein). One of these suppressors, SHM1, has been characterized at the molecular level and is described herein. SHM1 encodes a protein (SHM1p) that shares sequence similarity to a family of mitochondrial carrier proteins. On glycerol medium, where mitochondrial function is required for growth, shm1 deletion mutants are able to grow whereas shm1 abf2 double mutants are severely inhibited. These results suggest the SHM1p plays an accessory role to HM in the mitochondrion.