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Crystal structure of the Mus musculus cholesterol-regulated START protein 4 (StarD4) containing a StAR-related lipid transfer domain

Authors
  • Michael J. Romanowski
  • Raymond E. Soccio
  • Jan L. Breslow
  • Stephen K. Burley
Publisher
The National Academy of Sciences
Publication Date
May 14, 2002
Source
PMC
Keywords
Disciplines
  • Biology
License
Unknown

Abstract

The x-ray structure of the mouse cholesterol-regulated START protein 4 (StarD4) has been determined at 2.2-Å resolution, revealing a compact α/β structure related to the START domain present in the cytoplasmic C-terminal portion of human MLN64. The volume of the putative lipid-binding tunnel was estimated at 847 Å3, which is consistent with the binding of one cholesterol-size lipid molecule. Comparison of the tunnel-lining residues in StarD4 and MLN64-START permitted identification of possible lipid specificity determinants in both molecular tunnels. Homology modeling of related proteins, and comparison of the StarD4 and MLN64-START structures, showed that StarD4 is a member of a large START domain superfamily characterized by the helix-grip fold. Additional mechanistic and evolutionary studies should be facilitated by the availability of a second START domain structure from a distant relative of MLN64.

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