Subunit Association and Conformational Flexibility in the Head Subdomain of Human CD81 Large Extracellular Loop

• DOI: 10.1515/bc.2002.164
• Publication Date: 2004-10-20T14:26:52Z
• Authors: K. Kitadokoro; M. Ponassi; G. Galli; R. Petracca; F. Falugi; G. Grandi; M. Bolognesi
• Keywords: Models, Molecular; 0301 basic medicine; 0303 health sciences; Sequence Homology, Amino Acid; Protein Conformation; Molecular Sequence Data; Membrane Proteins; Hepacivirus; Crystallography, X-Ray; Protein Structure, Tertiary; Tetraspanin 28; 3. Good health; 03 medical and health sciences; Antigens, CD; Humans; Amino Acid Sequence; Pliability

The large extracellular loop of human CD81, a tetraspanin mediating hepatitis C virus envelope protein E2 binding to human cells, has been crystallized in a hexagonal form. The three-dimensional structure, solved and refined at 2.6 A resolution (R-factor = 22.8%), shows that the protein adopts a dimeric assembly, based on an association interface built up by tetraspanin-conserved residues. Structural comparisons with the tertiary structure of human CD81 large extracellular loop, previously determined in a different crystal form, show marked conformational fluctuations in the molecular regions thought to be involved in binding to the viral protein, suggesting rules for recognition and assembly within the tetraspan web.