Laser Flash-Induced Kinetic Analysis of Cytochrome f Oxidation by Wild-Type and Mutant Plastocyanin from the Cyanobacterium Nostoc sp. PCC 7119
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- 作者：Cristina Albarrá ; n ; José ; A. Navarro ; Fernando P. Molina-Heredia ; Piedad del S. Murdoch ; Miguel A. De la Rosa ; and Manuel Hervá ; s
- 刊名：Biochemistry
- 出版年：2005
- 出版时间：August 30, 2005
- 年：2005
- 卷：44
- 期：34
- 页码：11601 - 11607
- 全文大小：137K
- 年卷期：v.44,no.34(August 30, 2005)
- ISSN：1520-4995
文摘
Oxidation of the soluble, truncated form of cytochrome f by wild-type and mutant species ofplastocyanin has been analyzed by laser flash absorption spectroscopy in the cyanobacterium Nostoc(formerly, Anabaena) sp. PCC 7119. At low ionic strengths, the apparent electron transfer rate constantof cytochrome f oxidation by wild-type plastocyanin is 1.34 × 104 s-1, a value much larger than thosedetermined for the same proteins from other organisms. Upon site-directed mutagenesis of specific residuesat the plastocyanin interaction area, the rate constant decreases in all cases yet to varying extents. Theonly exception is the D54K variant, which exhibits a higher reactivity toward cytochrome f. In mostcases, the reaction rate constant decreases monotonically with an increase in ionic strength. The observedchanges in the reaction mechanism and rate constants are in agreement with the location of the mutatedresidues at the interface area, as well as with the peculiar orientation of the two partners within the Nostocplastocyanin-cytochrome f transient complex, whose NMR structure has been determined recently.Furthermore, the experimental data herein reported match well the kinetic behavior exhibited by thesame set of plastocyanin mutants when acting as donors of electrons to photosystem I [Molina-Heredia,F. P., et al. (2001) J. Biol. Chem. 276, 601-605], thus indicating that the copper protein uses the samesurface areas-one hydrophobic and the other electrostatic-to interact with both cytochrome f andphotosystem I.