1BSQ

STRUCTURAL AND FUNCTIONAL CONSEQUENCES OF POINT MUTATIONS OF VARIANTS A AND B OF BOVINE BETA-LACTOGLOBULIN

Summary for 1BSQ

• Entry DOI: 10.2210/pdb1bsq/pdb
• Descriptor: PROTEIN (BETA-LACTOGLOBULIN) (2 entities in total)
• Functional Keywords: bovine beta-lactoglobulin, genetic variants, point mutation, hydrophobic, hormone-growth factor complex, hormone/growth factor
• Biological source: Bos taurus (cattle)
• Total number of polymer chains: 1
• Total formula weight: 18301.17

Authors

Qin, B.Y.,Creamer, L.K.,Bewley, M.C.,Baker, E.N.,Jameson, G.B. (deposition date: 1998-08-29, release date: 1998-09-02, Last modification date: 2024-11-13)

Primary citation

Qin, B.Y.,Bewley, M.C.,Creamer, L.K.,Baker, E.N.,Jameson, G.B.
Functional implications of structural differences between variants A and B of bovine beta-lactoglobulin.
Protein Sci., 8:75-83, 1999

PubMed Abstract: The structure of the trigonal crystal form of bovine beta-lactoglobulin variant B at pH 7.1 has been determined by X-ray diffraction methods at a resolution of 2.22 A and refined to values for R and Rfree of 0.239 and 0.286, respectively. By comparison with the structure of the trigonal crystal form of bovine beta-lactoglobulin variant A at pH 7.1, which was determined previously [Qin BY et al., 1998, Biochemistry 37:14014-14023], the structural consequences of the sequence differences D64G and V118A of variants A and B, respectively, have been investigated. Only minor differences in the core calyx structure occur. In the vicinity of the mutation site D64G on loop CD (residues 61-67), there are small changes in main-chain conformation, whereas the substitution V118A on beta-strand H is unaccompanied by changes in the surrounding structure, thereby creating a void volume and weakened hydrophobic interactions with a consequent loss of thermal stability relative to variant A. A conformational difference is found for the loop EF, implicated in the pH-dependent conformational change known as the Tanford transition, but it is not clear whether this reflects differences intrinsic to the variants in solution or differences in crystallization.

PubMed: 10210185

Experimental method

X-RAY DIFFRACTION (2.22 Å)