Whitson P A, Matthews K S
Department of Biochemistry, Rice University, Houston, Texas 77251.
Biochemistry. 1987 Oct 6;26(20):6502-7. doi: 10.1021/bi00394a032.
The lactose repressor protein was chemically modified with 2,3-butanedione and phenylglyoxal. Arginine reaction was quantitated by either amino acid analysis or incorporation of 14C-labeled phenylglyoxal. Inducer binding activity was unaffected by the modification of arginine residues, while both operator and nonspecific DNA binding activities were diminished, although to differing degrees. The correlation of the decrease in DNA binding activities with the modification of approximately 1-2 equiv of arginine per monomer suggests increased reactivity of a functionally essential residue(s). For both reagents, operator DNA binding activity was protected by the presence of calf thymus DNA, and the extent of reaction with phenylglyoxal was simultaneously diminished. This protection presumably results from steric restriction of reagent access to an arginine(s) that is (are) essential for DNA binding interactions. These experiments suggest that there is (are) an essential reactive arginine(s) critical for repressor binding to DNA.
乳糖阻遏蛋白用2,3 - 丁二酮和苯乙二醛进行化学修饰。通过氨基酸分析或14C标记苯乙二醛的掺入来定量精氨酸反应。诱导剂结合活性不受精氨酸残基修饰的影响，而操纵基因和非特异性DNA结合活性均降低，尽管程度不同。每个单体约1 - 2当量精氨酸的修饰与DNA结合活性降低之间的相关性表明，一个或多个功能必需残基的反应性增加。对于这两种试剂，小牛胸腺DNA的存在可保护操纵基因DNA结合活性，同时与苯乙二醛的反应程度降低。这种保护可能是由于试剂接近对DNA结合相互作用至关重要的一个或多个精氨酸的空间限制所致。这些实验表明，存在一个或多个对阻遏蛋白与DNA结合至关重要的必需反应性精氨酸。
