Download MendeleyCrystal structure of human GM2-activator protein with a novel beta-cup topology.
Wright, C.S., Li, S.C., Rastinejad, F.(2000) J Mol Biol 304: 411-422
- PubMed: 11090283
- DOI: https://doi.org/10.1006/jmbi.2000.4225
- Primary Citation of Related Structures:
1G13 - PubMed Abstract:
GM2 activator protein (GM2-AP) belongs to a small group of non- enzymatic lysosomal proteins that act as cofactors in the sequential degradation of gangliosides. It has been postulated that GM2-AP extracts single GM2 molecules from membranes and presents them in soluble form to beta-hexosaminidase A for cleavage of N-acetyl-d-galactosamine and conversion to GM3. The high affinity of GM2-AP for GM2 is based on specfic recognition of the oligosaccharide moiety as well as the ceramide lipid tail. Genetic defects in GM2-AP result in an atypical form of Tay-Sachs disease known as variant AB GM2 gangliosidosis. The 2.0 A resolution crystal structure of GM2-AP reported here reveals a previously unobserved fold whose main feature is an eight-stranded cup-shaped anti-parallel beta-pleated sheet. The striking feature of the GM2-AP structure is that it possesses an accessible central hydrophobic cavity rather than a buried hydrophobic core. The dimensions of this cavity (12 Ax14 Ax22 A) are suitable for binding 18-carbon lipid acyl chains. Flexible surface loops and a short alpha-helix decorate the mouth of the beta-cup and may control lipid entry to the cavity.
Organizational Affiliation:
Department of Pharmacology, X-ray Crystallography Laboratory, University of Virginia, Charlottesville, VA 22908-0735, USA. csw2n@virginia.edu
