Crystal structures of bovine beta-lactoglobulin in the orthorhombic space group C2221 . Structural differences between genetic variants A and B and features of the Tanford transition

• DOI: 10.1046/j.1432-1327.2001.01918.x
• Publication Date: 2003-03-11T18:17:24Z
• Authors: Kesley M. G. Oliv...; Vera L. Valente-M...; Michelle M. Botelho; Lindsay Sawyer; Sergio T. Ferreira; Igor Polikarpov
• Keywords: Orthorhombic crystal system; BETA (programming language); Crystal (programming language)

The crystal structures of β‐lactoglobulin genetic variants A and B have been determined in the orthorhombic space group C2221 (lattice Y) by X‐ray diffraction at 2.0 Å and 1.95 Å resolution, respectively. The structural comparison shows that both variants exhibit the open conformation of the EF loop at the pH of crystallization (pH 7.9), in contrast to what has been reported for the same genetic variants at pH 7.1 in the trigonal space group P3221 (lattice Z) [Qin, B.Y., Bewley, M.C., Creamer, L.K., Baker, E.N. & Jameson, G.B. (1999) Protein Sci.8, 75–83]. Furthermore, it was found that the stereochemical environment of Tyr42 changes significantly with pH variation between pH 7 and pH 8. This may provide a structural explanation for an as yet unexplained feature of the Tanford transition, namely the increase in exposure of a tyrosine residue.