Structural analysis, fatty acid and thyroxine binding properties of Vancouver and Naskapi variants of human serum albumin.

ABSTRACT

OBJECTIVES: To purify and structurally identify two albumin variants found in the Canadian population of native Amerindian origin. To assess the ability of variant albumins to bind lauric acid and L-thyroxine. METHODS: The structural characterization of the alloalbumins was performed by conventional protein chemistry methods and by mass spectrometric analysis. Lauric acid and L-thyroxine affinities to variant albumins were assessed by kinetic dialysis and equilibrium dialysis techniques, respectively. RESULTS: The sequence investigations proved the two variants to be albumin Naskapi [372Lys --> Glu] and albumin Vancouver [501Glu --> Lys], respectively. Among the carriers of albumin Naskapi, we found a rare case of homozygosity. Furthermore, this is the first reported case of the 501Glu-->Lys mutation in the native North American population. Scatchard plot analysis revealed that the association constants for lauric acid and L-thyroxine to the two variants were indistinguishable from the endogenous form of albumin. CONCLUSION: We show that albumin variants Vancouver and Naskapi have normal fatty acid and L-thyroxine binding capabilities. These findings support the assumption that bisalbuminemias associated with these albumin variants are benign conditions.