Backbone structure of a small helical integral membrane protein: A unique structural characterization

Protein Sci. 2009 Jan;18(1):134-46. doi: 10.1002/pro.24.

Abstract

The structural characterization of small integral membrane proteins pose a significant challenge for structural biology because of the multitude of molecular interactions between the protein and its heterogeneous environment. Here, the three-dimensional backbone structure of Rv1761c from Mycobacterium tuberculosis has been characterized using solution NMR spectroscopy and dodecylphosphocholine (DPC) micelles as a membrane mimetic environment. This 127 residue single transmembrane helix protein has a significant (10 kDa) C-terminal extramembranous domain. Five hundred and ninety distance, backbone dihedral, and orientational restraints were employed resulting in a 1.16 A rmsd backbone structure with a transmembrane domain defined at 0.40 A. The structure determination approach utilized residual dipolar coupling orientation data from partially aligned samples, long-range paramagnetic relaxation enhancement derived distances, and dihedral restraints from chemical shift indices to determine the global fold. This structural model of Rv1761c displays some influences by the membrane mimetic illustrating that the structure of these membrane proteins is dictated by a combination of the amino acid sequence and the protein's environment. These results demonstrate both the efficacy of the structural approach and the necessity to consider the biophysical properties of membrane mimetics when interpreting structural data of integral membrane proteins and, in particular, small integral membrane proteins.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Escherichia coli / metabolism
  • Membrane Proteins / chemistry*
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Micelles
  • Models, Molecular
  • Mycobacterium tuberculosis / genetics*
  • Nuclear Magnetic Resonance, Biomolecular
  • Protein Conformation
  • Protein Structure, Tertiary / genetics
  • Recombinant Fusion Proteins / chemistry*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Reproducibility of Results
  • Spin Labels
  • Statistics as Topic

Substances

  • Bacterial Proteins
  • Membrane Proteins
  • Micelles
  • Recombinant Fusion Proteins
  • Spin Labels