IS IT POSSIBLE THE DIRECT ENERGY TRANSFER FROM THE LHII TO THE CR IN THE ABSENCE OF LHI ANTENNA COMPLEX?.

LAURA J. RAIGER-IUSTMAN; MARC J. BORNMANN; SIMON KOHLER; ANDREAS LABAHN; NORMA L. PUCHEU; NORMA L. KERBER; AUGUSTO F. GARCIA

Iguazú , Misiones

Congreso; XL Reunión anual de la Sociedad Argentina en investigación en Bioquímica y Biología Molecular; 2004

SAIB

There are different results on the effectiveness of energy transfer from the peripheral light-harvesting (LH) complex 2 directly to the reaction center (RC) in mutant strains lacking the core LH1 complex. A LH1- mutant of Rhodovulum sulfidophilum, named rsLRI, was constructed by deleting the puf A and B genes, resulting in a Kanamycin resistant greenish-brown, photosynthetically positive clone. Under photosynthetic conditions, those cells grew only at high-light intensities (500 Wm-2). Below this value the efficiency of photosynthetic growth decreases and at 50 Wm-2 no photosynthetic growth was observed. The wild type phenotype was completely restored by inserting in trans a DNA segment containing the puf A and B genes. Light-induced FTIR difference spectra of wild type and rsLRI showed to have only marginal differences, indicating no large structural changes of the RC due to the deletion of LH1. The amount of RC in each strain was similar, according the bleaching of the absorption band at 865 nm (DA865, is indicative for the P®P+ transition in the reaction center) These results are interpreted as indicating that energy transfer between LH2 and RC is inefficient. It is possible that most of the energy necessary for photosynthetic growth was provided by light harvested directly by the RC.