Tim44 is an essential component of the machinery that mediates the translocation of nuclear-encoded proteins across the mitochondrial inner membrane [1]. Tim44 is thought to bind phospholipids of the mitochondrial inner membrane both by electrostatic interactions and by penetrating the polar head group region [1]. This family includes the C-terminal region of Tim44 that has been shown to form a stable proteolytic fragment in yeast. This region is also found in a set of smaller bacterial proteins. The molecular function of the bacterial members of this family is unknown but transport seems likely. The crystal structure of the C terminal of Tim44 has revealed a large hydrophobic pocket which might play an important role in interacting with the acyl chains of lipid molecules in the mitochondrial membrane [3].

1: Domain structure and lipid interaction of recombinant yeast Tim44. Weiss C, Oppliger W, Vergeres G, Demel R, Jeno P, Horst M, de Kruijff B, Schatz G, Azem A; Proc Natl Acad Sci U S A 1999;96:8890-8894. PMID:10430866

2: Preliminary crystallographic studies of yeast mitochondrial peripheral membrane protein Tim44p. Josyula R, Jin Z, McCombs D, DeLucas L, Sha B; Acta Crystallograph Sect F Struct Biol Cryst Commun. 2006;62:172-174. PMID:16511294

3: Crystal structure of yeast mitochondrial peripheral membrane protein Tim44p C-terminal domain. Josyula R, Jin Z, Fu Z, Sha B; J Mol Biol. 2006;359:798-804. PMID:16647716