Methionine-90-spin-labeled bovine alpha-lactalbumin: electron spin resonance and NMR distance measurements.
Methionine-90-spin-labeled bovine alpha-lactalbumin: electron spin resonance and NMR distance measurements.
复制标题
蛋氨酸-90-自旋标记的牛 α-乳清蛋白：电子自旋共振和 NMR 距离测量。
DOI：
10.1021/bi00404a028
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发表时间：
1988
期刊：
影响因子：
2.9
通讯作者：
Berliner,LJ
中科院分区：
文献类型：
--
作者：
Musci,G;Koga,K;Berliner,LJ
Department of Chemistry, The Ohio State University, 120 West 18th Avenue, Columbus, Ohio 43210 Received June 19, 1987; Revised Manuscript Received October 5, 1987 abstract: The unique methionine residue of bovine-lactalbumin was modified by irreversible alkylation with the bromoacetamido nitroxide spin-label 4-(2-bromoacetamido)-2, 2, 6, 6-tetramethylpiperidine-iV-oxyl. The line shape of the electron spin resonance(ESR) spectrum was indicative of a fairly mobile spin-label and was sensitive to the calcium-induced conformational change. Paramagnetic broadening of the spin-label ESR lines by a Gd (III) ion substituted at the high-affinity calcium site of the protein yielded a distance between the spin-label and the metal-binding site of 8.0±1.0 Á. The extent of the paramagnetic line broadening by the covalently attached nitroxide spin-label on the proton resonances of several amino acid residues of the protein at 500 MHz allowed estimation of intramolecular distances between the methionine-90 residue and several resolvable protons. a-Lactalbumin (-LA) 1 is the regulatory subunit of the “lactose synthase” complex. Upon binding to the enzyme galactosyltransferase (EC 2.4. 1.22), lactose is efficiently synthesized from UDP-galactose and glucose. A putative, energy-minimized, three-dimensional structure was proposed by Warme et al.(1974) which was based, in part, on the high degree of primary structure homology between-LA and lysozyme (Brew et al., 1970; Shewale et al., 1985). More recently, Smith et al.(1987) have reported a low-resolution crystallographic analysis of baboon-LA, which, while not at the precise atomic resolution of most protein structures, confirmed that-LA probably evolved from a lysozyme pre-cursor. In spite of their structural similarities, the latter two proteins are quite functionally and physicochemically different. In particular,-lactalbumin is a metalloprotein, with high affinities for Ca (II)(Permyakov et al., 1981, 1985; Murakami et al., 1982) and Zn (II)(Murakami et al., 1982; Musci &
