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Updated: Aug 15, 2026

Assessment of Immunologically Relevant Dynamic Tertiary Structural Features of the HIV-1 V3 Loop Crown R2 Sequence by ab initio Folding
Published on: September 15, 2010
Mutations in a potential phospholipid binding loop in the C2 domain of factor V affecting the assembly of the
G A Nicolaes1, B O Villoutreix, B Dahlbäck
1The Wallenberg Laboratory, Department of Clinical Chemistry, University Hospital Malmö, Lund University, Sweden. Gerry.Nicolaes@klkemi.mas.lu.se
Abstract:
Activated factor V (FVa) serves as a cofactor to activated factor X in the prothrombinase complex. FVa is homologous to activated factor VIII (FVIIIa), the light chains of both proteins being formed by similar domains (A3-C1-C2). Interaction of FVa and FVIIIa with negatively charged phospholipid membranes is crucial for the function of both cofactors. In both proteins, the C2 domains are important for membrane binding but a detailed understanding of the binding mechanisms is missing. Recently, knowledge has been gained into the three-dimensional structures of the C domains facilitating studies of structure-function relationships. Structural analysis of the C2 domain in FVa predicted a surface-exposed loop (K2060, K2061, S2062, W2063, W2064) to be involved in membrane binding. Three double mutants were created, K2060Q-K2061Q, W2063Y-W2064Y and W2063A-W2064A, and expressed in a transient expression system. In addition, a FV variant in which all four residues were mutated, K2060Q-K2061Q-W2063A-W2064A, was produced. Mutagenesis of the two lysines showed no functional consequences, whereas mutagenesis of the two tryptophanes yielded FVa with impaired ability to interact with the phospholipid, as demonstrated by a poor functional activity at limiting phospholipid concentrations. A molecular model of FVa, anchored at the surface of a phospholipid membrane, was developed and used as a template for the interpretation of the mutagenesis experiments.
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