晶体结构dihaem细胞色素c4的假单胞菌stutzeri 2.2决议决定。
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Kadziola,拉森
晶体结构dihaem细胞色素c4的假单胞菌stutzeri 2.2决议决定。
结构。1997年2月15日,5 (2):203 - 16。
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9032080 (在PubMed]
- 文摘
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背景:。细胞色素c4 dihaem是细胞色素c见于多种细菌。他们认为参与电子传递系统与有氧和无氧呼吸。细胞色素c4蛋白位于周质,主要是绑定到内心的膜,并能减少之间的电子转移膜结合系统和终端氧化酶类。对齐的细胞色素c4序列从三个细菌,铜绿假单胞菌、假单胞菌stutzeri和固氮菌vinelandii,表明这些dihaem蛋白质是由两个相似的域名。两个截然不同的氧化还原电位的测量Ps. stutzeri细胞色素c4,然而。结果:。dihaem细胞色素c4的晶体结构从Ps. stutzeri 2.2决心解决了同形替换。模型,包括两个完整的细胞色素c4分子和138个水分子不对称单位,精制的R值20.1%所有观测决议范围8 - 2.2。分子被组织在两个细胞色素c pseudo-twofold轴相关的领域。 The symmetry is virtually perfectly close to the twofold axis, which passes through a short hydrogen bond between the two haem propionic acid groups, connecting the redox centre of each domain. This haem-haem interaction is further stabilized by an extensive symmetrical hydrogen-bond network. The twofold symmetry is not present further away from the axis, however, and the cytochrome c4 molecule can be considered to be a dipole with charged residues unevenly distributed between the two domains. The haem environment in the two domains show pronounced differences, mainly on the methionine side of the haem group. CONCLUSIONS: . The structure, in conjunction with sequence alignment, suggests that the cytochrome protein has evolved by duplication of a cytochrome c gene. The difference in charge distribution around each haem group in the two domains allows the haem group in the N-terminal domain to be associated with the lower redox potential of 241 mV and the C-terminal haem group with the higher potential of 328 mV. The molecular dipole characteristic of cytochrome c4 is important for its interaction with, and recognition of, its redox partners. In cytochrome c4, the hydrogen-bond network (between residues that are conserved in all known cytochrome c4 subspecies) seems to provide an efficient pathway for an intramolecular electron transfer that can ensure cooperativity between the two redox centres. The C-pyrrole corners of the haem edges are potential sites for external electron exchange.