The complex of cytochrome f and plastocyanin from Nostoc sp. PCC 7119 is highly dynamic.
Bottom Line: The complex from Nostoc sp.Chemical-shift-perturbation analysis showed that the presence of spin labels on the surface of Cyt f does not significantly affect the binding of Pc.The paramagnetic relaxation enhancement results are not consistent with a single orientation of Pc, thus indicating that multiple orientations must occur and suggesting that an encounter state represents a large fraction of the complex.
Affiliation: Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands.Show MeSH
Mentions: To study the complex of Cyt f and Pc with PRE NMR spectroscopy,three sites for probe attachment were selected. The positions of the mutationswere selected on the basis of the solution structure of the wild-type complex asdetermined by NMR spectroscopy, on the basis of PCS and chemical shiftperturbations. The rationale ofthe work followed that of Volkov et al.for the complex of CcP and Cyt c, that is, to obtainconstraints for structure determination and to improve the precision of thesolution structure that was based on PCS. Residues N71, Q104, and S192, whichare located around the Pc binding site, were mutated to cysteine (Figure 1). In order to preserve theoverall electrostatic potential in the complex only polar, uncharged amino acidresidues were selected.
Affiliation: Institute of Chemistry, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands.