Structure of the Complex between Plastocyanin and Cytochrome f from the Cyanobacterium Nostoc sp. PCC 7119 as Determined by Paramagnetic NMR

Abstract

The complex between cytochrome f and plastocyanin from the cyanobacterium Nostoc has been characterized by NMR spectroscopy. The binding constant is 16 mM ؊1 , and the lifetime of the complex is much less than 10 ms. Intermolecular pseudo-contact shifts observed for the plastocyanin amide nuclei, caused by the heme iron, as well as the chemical-shift perturbation data were used as the sole experimental restraints to determine the orientation of plastocyanin relative to cytochrome f with a precision of 1.3 Å. The data show that the hydrophobic patch surrounding tyrosine 1 in cytochrome f docks the hydrophobic patch of plastocyanin. Charge complementarities are found between the rims of the respective recognition sites of cytochrome f and plastocyanin. Significant differences in the relative orientation of both proteins are found between this complex and those previously reported for plants and Phormidium, indicating that electrostatic and hydrophobic interactions are balanced differently in these complexes.

An NMR‐based docking model for the physiological transient complex between cytochrome f and cytochrome c6

“…Also, the ET between the soluble domain of cytochrome f (Cf) and Pc has been studied extensively [1], highlighting the role of electrostatic and hydrophobic interactions in binding [1]. NMR studies have enabled the determination of the relative orientations of Pc and Cf in several Pc-Cf complexes [5][6][7][8][9][10]. These studies demonstrate that the position of Pc within the complex is dependent on the extent of electrostatic interactions.…”

“…PCC 7119 Cc 6 was purified as described [10] from Escherichia coli cells transformed with both pEAC-WT [15] and pEC86 [16] plasmids. Production and purification of the soluble domain of Nostoc sp.…”

The Electron Transfer Complex between Cytochrome c552 and the CuA Domain of the Thermus thermophilus ba3 Oxidase

“…5 This transient nature of the redox interaction precludes the detection of any intermolecular NOE connectivities to define the contact region between the proteins. However, the highly sensitive amide resonances allow the observation of chemical shift changes as a result of transient alterations in the local environment due to the presence of the redox partner, as previously demonstrated with other systems such as plastocyanin/cytochrome c, plastocyanin/cytochrome f, cytochrome c peroxidase/iso-1-cytochrome c, and Cu A domain/cytochrome c 552 from P. denitrificans for example (19,(21)(22)(23).…”

La evolución biológica a nivel molecular

“…Al final de la evolución, las plantas superiores sólo producen plastocianina (4). La sustitución funcional de una proteína por otra es posible, a pesar de su diferencia estructural, porque ambas poseen el mismo potencial redox y punto isoeléctrico, así como áreas superficiales electrostáticas e hidrófobas equivalentes que les permiten reconocer e interaccionar con los mismos complejos de membrana (5,6). Se trata, por tanto, de un caso paradigmático de evolución convergente, a nivel molecular, gobernado por las condiciones geoquímicas cambiantes, es decir, por las biodisponibilidades relativas de ciertos elementos metálicos (3,5).…”