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The nitrogen source-dependent 126-kDa protein from Synechococcus PCC 7942 plasmalemma: a trimer of the NrtA
C Fresneau1, M Zinovieva, D Blanot
1Laboratoire de Bioénergétique Membranaire, A.N. Bakh Institute of Biochemistry, Russian Academy of Science, Moscow. chantal.fresneau@bioen.u-psud.fr
Abstract:
Expression of a 126-kDa protein in the plasmalemma (cytoplasmic membrane) from Synechococcus PCC 7942 is dependent on the nitrogen source. Polyclonal antibody raised against the NrtA protein reacted with the 126-kDa protein. Two peptide sequences from the 126-kDa protein were retrieved in NrtA. FPLC purification of plasmalemma solubilised in Triton X-100 gave a fraction consisting mainly of a 126-kDa component (72.6%), as shown by sedimentation velocity. Equilibrium sedimentation of the same fraction gave evidence of the existence of an oligomeric structure (Ka = 2 x 10(3) and 2.9 subunits). Thus, the 126-kDa protein is considered as a trimeric arrangement of the 45-kDa protein in the plasmalemma.