EXAFS STUDIES OF THE NITROGENASE IRON PROTEIN FROM AZOTOBACTER-VINELANDII
EXAFS STUDIES OF THE NITROGENASE IRON PROTEIN FROM AZOTOBACTER-VINELANDII
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DOI：
10.1021/ic00270a018
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发表时间：
1987-11-18
影响因子：
4.6
通讯作者：
ORMEJOHNSON, WH
中科院分区：
文献类型：
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作者：
LINDAHL, PA;TEO, BK;ORMEJOHNSON, WH
我们最近发现，[4Fe-4S]+团簇的铁蛋白可以存在于S=*/2，-S=* 3/2，可能S= S/2自旋状态，这取决于溶剂和蛋白质的核苷酸结合位点的占用。我们用EXAFS技术研究了还原态（1+）和氧化态（2+）、S ′ =*/2和S= 3/2自旋态以及MgATP束缚态的团簇结构。在2.31（1.5）μ m处计算的蛋白质数据的平均Fe-S配位数为4.0（5），Debye-Waller因子为0.06（1）μ m。该簇可能通过四个硫（半胱氨酸）配体与蛋白质结合。氧化合成簇和还原Fe蛋白簇的平均Fe-S距离存在显著差异。MgATP诱导的构象变化和S=*/2到S= 3/2的自旋态转换都不需要平均Fe-S键长的变化超过0.02 μ m。蛋白质数据的平均计算Fe-Fe配位数为2.4（8），距离为2.73（3）nm。Fe蛋白质数据的Fe-Fe项的Debye-Waller因子（0.10（2）μ m）大于模型簇数据的Debye-Waller因子（0.08 μ m），这种差异导致了对Fe蛋白质簇中Fe-Fe配位数的低估。
We have recently shown that the [4Fe-4S]+ cluster of the iron protein can exist in S=*/2,-S=* 3/2, and probably S= s/2 spin states, depending on the solvent and on the occupancy of the protein’s nucleotide binding sites. We have now examined the structure of the cluster in thereduced (1+) and oxidized (2+) electronic states, the S'=*/2 and S= 3/2 spin states, andin the MgATP-bound form by using the EXAFS technique. Theaverage calculated Fe-S coordination number for the protein data is 4.0 (5) at a distance of 2.31 (1.5) Á with a Debye-Waller factor of 0.06 (1) Á. The cluster is probably bound to the protein via four sulfur (cysteine) ligands. Significant differences in the average Fe-S distance of oxidized synthetic clusters and reducedFe protein clusters were observed. Neither the MgATP-induced conformational change nor the S=*/2 to S= 3/2 spin-state conversion requires changes in theaverage Fe-S bond length of more than about 0.02 Á. The average calculated Fe-Fe coordination number for the protein data is 2.4 (8), at a distance of 2.73 (3) Á. The Debye-Waller factor for the Fe-Fe term of the Fe protein data (0.10 (2) Á) is larger than that for the model cluster data (0.08 Á), and this dissimilarity results in an underestimate of the Fe-Fe coordination number in the Fe protein cluster.