The intermembrane space domain of Tim23 is intrinsically disordered with a distinct binding region for presequences

Protein Sci. 2010 Nov;19(11):2045-54. doi: 10.1002/pro.482.

Abstract

Proteins targeted to the mitochondrial matrix are translocated through the outer and the inner mitochondrial membranes by two protein complexes, the translocase of the outer membrane (TOM) and one of the translocases of the inner membrane (TIM23). The protein Tim23, the core component of TIM23, consists of an N-terminal, soluble domain in the intermembrane space (IMS) and a C-terminal domain that forms the import pore across the inner membrane. Before translocation proceeds, precursor proteins are recognized by the N-terminal domain of Tim23, Tim23N (residues 1-96). By using NMR spectroscopy, we show that Tim23N is a monomeric protein belonging to the family of intrinsically disordered proteins. Titrations of Tim23N with two presequences revealed a distinct binding region of Tim23N formed by residues 71-84. In a charge-hydropathy plot containing all soluble domains of TOM and TIM23, Tim23N was found to be the only domain with more than 40 residues in the IMS that is predicted to be intrinsically disordered, suggesting that Tim23N might function as hub in the mitochondrial import machinery protein network.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Circular Dichroism
  • Membrane Transport Proteins / chemistry*
  • Membrane Transport Proteins / genetics
  • Membrane Transport Proteins / metabolism
  • Models, Molecular
  • Molecular Sequence Annotation
  • Molecular Sequence Data
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Structure, Tertiary
  • Protein Transport
  • Saccharomyces cerevisiae Proteins / chemistry*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism

Substances

  • Membrane Transport Proteins
  • Saccharomyces cerevisiae Proteins
  • TIM23 protein, S cerevisiae