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The Role of Tim9p in the Assembly of the TIM22 Import Complexes
Author(s) -
Leuenberger Danielle,
Curran Sean P.,
Wong David,
Koehler Carla M.
Publication year - 2003
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1034/j.1600-0854.2003.00095.x
Subject(s) - biology , mutant , mitochondrion , microbiology and biotechnology , transport protein , membrane protein , inner mitochondrial membrane , inner membrane , biochemistry , membrane , gene
Tim9p is located in the soluble 70‐kDa Tim9p–Tim10p complex and the 300‐kDa membrane complex in the mitochondrial TIM22 protein import system, which mediates the import of inner membrane proteins. From a collection of temperature‐sensitive mutants, we have analyzed two in detail. tim9–3 contained two mutations and tim9–19 contained one mutation, all located near the ‘twin CX 3 C’ motif that is conserved in the small Tim proteins. As a result, the import components in the tim9–3 mutant mitochondria were severely reduced and assembled into complexes of aberrant sizes. Protein import was severely reduced and Tim9p and Tim10p binding to in vitro imported ADP/ATP carrier was impaired. In the tim9–19 mutant mitochondria, the 300‐kDa membrane complex was assembled, although the soluble 70‐kDa Tim9p–Tim10p complex was not detectable. Protein import was decreased only two‐fold. When coexpressed in Escherichia coli , tim9–19 and TIM10 proteins failed to assemble into a 70‐kDa complex. Our findings suggest that residues near the ‘twin CX 3 C’ motif are important for the assembly of Tim9p in both the Tim9p–Tim10p complex and the 300‐kDa membrane complex.