SSC1, SSQ1, and ECM10 encode chaperone proteins of the HSP70 family that localize to the mitochondria (2 and reviewed in 5). In addition to these three mitochondrial HSP70s, S. cerevisiae cells also synthesize nine cytosolic HSPs (encoded by SSA1, SSA2, SSA3, SSA4, SSB1, SSB2, SSE1, SSE2, SSZ1) and two that are found in the ER (KAR2, LHS1). HSP70 is a large family of proteins that has been evolutionarily conserved from bacteria (DnaK) to humans (HSP72/73). HSP70 proteins were originally classified based upon their induction by heat shock and their size of ~70kDa. The main function of these proteins is to serve as molecular chaperones, binding unfolded peptides to assist in proper folding and prevent aggregation/misfolding (reviewed in 6 and 7). HSP70s are also involved in disassembling aggregates of misfolded proteins, translocating select proteins into the mitochondria and ER, and degrading aberrant proteins (reviewed in 8, 7, and 6).

ECM10 was originally identified in a screen for genes involved in cell wall biogenesis (1). Ecm10p localizes to mitochondrial nucleoids and is suggested to function in mitochondrial protein import (3, 2). Ecm10p displays a high degree of similarity to the other mitochondrial HSP70 proteins (82% and 54% amino acid identity with Ssc1p and Ssq1p, respectively) and like all HSP70s, has an N-terminal ATPase domain and a C-terminal peptide-binding domain (2). Like Ssc1p and Ssq1p, Ecm10p interacts with the nucleotide exchange factor Mge1p in an ATP-dependent manner (2, 9). Overexpression of Ecm10p results in extensive mitochondrial DNA aggregations. While ecm10 deletion mutants are viable, ecm10 ssc1 double null mutants exhibit synthetic growth defects (3, 2).

Last updated: 2006-02-09