mitochondrial import inner membrane translocase subunit TIM9A (TIMM9, TIM9, TIM9A, TIMM9A)

Function

• mitochondrial intermembrane chaperone
• participates in the import & insertion of multi-pass transmembrane proteins into the mitochondrial inner membrane
• may also be required for transfer of beta-barrel precursors from the TOM complex to the sorting & assembly machinery (SAM complex) of the outer membrane
• acts as a chaperone-like protein that protects the hydrophobic precursors from aggregation & guides them through the mitochondrial intermembrane space
• forms heterohexamer; composed of 3 copies of TIMM9 & 3 copies of TIMM10/TIM10A, named soluble 70 kD complex; the complex forms a 6-bladed alpha-propeller structure & associates with the TIMM22 component of the TIM22 complex
• interacts with multi-pass transmembrane proteins in transit
• also forms a complex composed of TIMM9, TIMM10/TIM10A & FXC1/TIM10B

Structure

• the twin CX3C motif contains 4 conserved Cys that form 2 disulfide bonds in the mitochondrial intermembrane space
• however, during the transit of TIMM9 from cytoplasm into mitochondrion, the Cys probably coordinate Zn+2, thus preventing folding & allowing its transfer across the mitochondrial outer membrane
• belongs to the small Tim family

Compartment

• mitochondrial inner membrane, intermembrane side

Expression

• ubiquitous
• highest expression in heart, kidney, liver & skeletal muscle

More general terms

• protein subunit
• mitochondrial membrane protein

Component of

• mitochondrial import inner membrane translocase subunit (TIM, translocase of inner mitochondrial membrane, mitochondrial protein importer)

Database

• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:2652
• OMIM: https://mirror.omim.org/entry/607384
• UniProt: http://www.uniprot.org/uniprot/Q9Y5J7.html