tailieunhanh - Báo cáo khoa học: Role of the surface charges D72 and K8 in the function and structural stability of the cytochrome c6 from Nostoc sp. PCC 7119

We investigated the role of electrostatic charges at positions D72 and K8 in the function and structural stability of cytochrome c6 from Nostocsp. PCC 7119 (cytc6). A series of mutant forms was generated to span the possible combinations of charge neutralization (by mutation to alanine) and charge inversion (by mutation to lysine and aspartate, respectively) in these positions. | ềFEBS Journal Role of the surface charges D72 and K8 in the function and structural stability of the cytochrome c6 from Nostoc sp. PCC 7119 Christian Lange1 Irene Luque2 Manuel Hervas1 Javier Ruiz-Sanz2 Pedro L. Mateo2 and Miguel A. De la Rosa1 1 Institute de Bioquimica Vegetaly Fotosintesis Centro de Investigaciones Cientificas Isla de la Cartuja Seville Spain 2 Departamento de Quimica Fisica e Instituto de Biotecnologia Universidad de Granada Spain Keywords cytochrome c6 electron transfer electrostatic interactions protein folding protein stability Correspondence Christian Lange Martin-Luther-Universitat Halle Wittenberg Institut fur Biotechnologie Kurt-Mothes-Str. 3 06120 Halle Saale Germany Fax 49 345 552 7013 Tel 49 345 552 4948 E-mail . Received 10 February 2005 revised 21 April2005 accepted 3 May 2005 doi We investigated the role of electrostatic charges at positions D72 and K8 in the function and structural stability of cytochrome c6 from Nostoc sp. PCC 7119 cyt c6 . A series of mutant forms was generated to span the possible combinations of charge neutralization by mutation to alanine and charge inversion by mutation to lysine and aspartate respectively in these positions. All forms of cyt c6 were functionally characterized by laser flash absorption spectroscopy and their stability was probed by urea-induced folding equilibrium relaxation experiments and differential scanning calorimetry. Neutralization or inversion of the positive charge at position K8 reduced the efficiency of electron transfer to photosystem I. This effect could not be reversed by compensating for the change in global charge that had been introduced by the mutation indicating a specific role for K8 in the formation of the electron transfer complex between cyt c6 and photosystem I. Replacement of D72 by asparagine or lysine increased the efficiency of electron transfer to photosystem I but destabilized the protein.