Khamis M I, Casas-Finet J R, Maki A H, Murphy J B, Chase J W
J Biol Chem. 1987 Aug 15;262(23):10938-45.
Fluorescence and optical detection of triplet state magnetic resonance (ODMR) spectroscopy have been employed to study the complexes formed between single-stranded polynucleotides and Escherichia coli ssb gene products (SSB) in which tryptophans 40, 54, and 88 are selectively, one residue at a time, replaced by phenylalanine using site-specific oligonucleotide mutagenesis. Fluorescence titrations and ODMR results indicate that tryptophans 40 and 54 are the only tryptophan residues in E. coli single-stranded DNA binding protein that are involved in stabilizing the protein-nucleic acid complexes via stacking interactions. Wavelength-selected ODMR measurements on E. coli SSB reveal the presence of two spectrally distinct tryptophan sites (Khamis, M. I., Casas-Finet, J. R., and Maki, A. H. (1987) J. Biol. Chem. 262, 1725-1733). Our present results indicate that tryptophan 54 belongs to the blue-shifted site, while tryptophan 40 belongs to the red-shifted site of the protein.
利用荧光和三线态磁共振光检测（ODMR）光谱法研究了单链多核苷酸与大肠杆菌单链DNA结合蛋白（SSB）基因产物形成的复合物，其中色氨酸40、54和88通过位点特异性寡核苷酸诱变，每次一个残基被苯丙氨酸选择性取代。荧光滴定和ODMR结果表明，色氨酸40和54是大肠杆菌单链DNA结合蛋白中仅有的通过堆积相互作用参与稳定蛋白质-核酸复合物的色氨酸残基。对大肠杆菌SSB进行的波长选择ODMR测量揭示了存在两个光谱上不同的色氨酸位点（Khamis，M. I.，Casas-Finet，J. R.，和Maki，A. H.（1987）J. Biol. Chem. 262，1725 - 1733）。我们目前的结果表明，色氨酸54属于该蛋白蓝移位点，而色氨酸40属于红移位点。
