Narayan M, Berliner L J
Ohio State University Biophysics Program, Columbus 43210, USA.
Biochemistry. 1997 Feb 18;36(7):1906-11. doi: 10.1021/bi9621526.
beta-Lactoglobulin (Big) binds 1 mol of a fatty acid spin-label analog, 5-doxylstearic acid (5-DSA), per mole of protein with a dissociation constant Kd = 0.8 microM for the strongest binding site. There are also several weaker sites for this ligand. Blg saturated with either retinol or retinoic acid binds 5-DSA with essentially equal affinity (Kd = 0.6 and 1 microM, respectively). Palmitic acid and SDS displace bound 5-DSA from Blg. However, unlike palmitic acid, 5-DSA binding does not enhance the structural stability of Blg to urea denaturation. The spin-labeled fatty acid also binds to the protein at low pH, presumably at secondary fatty acid binding sites. These results suggest that Blg binds at least two different types of hydrophobic ligands simultaneously.
β-乳球蛋白（Blg）每摩尔蛋白质可结合1摩尔脂肪酸自旋标记类似物5-硬脂酸（5-DSA），最强结合位点的解离常数Kd = 0.8 μM。该配体还有几个较弱的结合位点。用视黄醇或视黄酸饱和的Blg与5-DSA结合的亲和力基本相等（Kd分别为0.6和1 μM）。棕榈酸和十二烷基硫酸钠（SDS）可将结合在Blg上的5-DSA置换下来。然而，与棕榈酸不同的是，5-DSA的结合不会增强Blg对尿素变性的结构稳定性。自旋标记的脂肪酸在低pH值下也能与该蛋白质结合，推测是在二级脂肪酸结合位点。这些结果表明，Blg可同时结合至少两种不同类型的疏水配体。
