TY - JOUR
T1 - Functional implications of structural differences between variants A and B of bovine β-lactoglobulin
AU - Qin, Bin Y.
AU - Bewley, Maria C.
AU - Creamer, Lawrence K.
AU - Baker, Edward N.
AU - Jameson, Geoffrey B.
PY - 1999
Y1 - 1999
N2 - The structure of the trigonal crystal form of bovine β-lactoglobulin variant B at pH 7.1 has been determined by X-ray diffraction methods at a resolution of 2.22 Å and refined to values for R and R(free) of 0.239 and 0.286, respectively. By comparison with the structure of the trigonal crystal form of bovine β-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 β-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.
AB - The structure of the trigonal crystal form of bovine β-lactoglobulin variant B at pH 7.1 has been determined by X-ray diffraction methods at a resolution of 2.22 Å and refined to values for R and R(free) of 0.239 and 0.286, respectively. By comparison with the structure of the trigonal crystal form of bovine β-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 β-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.
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U2 - 10.1110/ps.8.1.75
DO - 10.1110/ps.8.1.75
M3 - Article
C2 - 10210185
AN - SCOPUS:0032923417
SN - 0961-8368
VL - 8
SP - 75
EP - 83
JO - Protein Science
JF - Protein Science
IS - 1
ER -