An X-ray absorption study of chemically modified bacterial photosynthetic reaction centers
نویسندگان
چکیده
Local structures around metal atoms in Hi and Zn substituted 132-hydroxy-bacteriochlorophyll a (Ni-HOB, and Zn-HOB) with and without insertion into the accessory bacteriochlorophyll a (BChla) sites in Rhodobacter sphaeroides photosynthetic reaction centers (RC) are studied using X-ray absorption spectroscopy. The penta-coordination of Ni-HOB and Zn-HOB in the RC is similar to that of BChl a in native RC, where the fifth ligandis from a nearby histidine residue. Average Ni-N and Zn-N distances increase by 0.08 .~ in Ni-HOB and decrease by 0.04 A in Zn-HOB-Et20 as the modified chlorophylls bind with the RC due to the interaction between the protein and the macrocycle.
منابع مشابه
CHEMICALLY MODIFIED PHOTOSYNTHETIC BACTERIAL REACTION CENTERS: CIRCULAR DICHROISM, RAMAN RESONANCE, LOW TEMPERATURE ABSORPTION, FLUORESCENCE AND ODMR SPECTRA AND POLYPEPTIDE COMPOSITION OF BOROHYDRIDE TREATED REACTION CENTERS FROM Rhodobacter sphaeroides
Reaction centers from Rhodobacter sphaeroides have been modified by treatment with sodium borohydride similar to the original procedure [Ditson el al . , Biochim. Biophys. Acta 766, 623 (1984)], and investigated spectroscopically and by gel electrophoresis. (1) Low temperature (1.2 K) absorption, fluorescence, absorptionand fluorescence-detected ODMR, and microwave-induced singlet-triplet absor...
متن کاملMinireview Research on photosynthetic reaction centers from 1932 to 1987
The history of research on photosynthetic reaction centers is outlined, starting with the implication of their existence through the discovery of the photosynthetic unit, as reported by R. Emerson and W. Arnold in 1932, and culminating in the crystallization and X-ray analysis of the anoxygenic bacterial reaction centers, reported by J. Deisenhofer, H. Michel, and coworkers, over the period 198...
متن کاملModification of pigment composition in the isolated reaction center of photosystem II.
The pigment content of isolated reaction centers of photosystem II was modified using an exchange protocol similar to that used for purple bacterial reaction centers. With this method, which is based on incubation of reaction centers at elevated temperature with an excess of chemically modified pigments, it was possible to incorporate [3-acetyl]-chlorophyll a and [Zn]-chlorophyll a into photosy...
متن کاملTime-resolved spectroscopy of the primary photosynthetic processes of membrane-bound reaction centers from an antenna-deficient mutant of Rhodobacter capsulatus
The primary photosynthetic reactions in whole membranes of the antenna-deficient mutant strain U43 (pTXA6-10) of Rhodobacter capsulatus are studied by transient absorption and emission spectroscopy with subpicosecond time resolution. Extensive similarities between the transient absorption data on whole membranes and on isolated reaction centers support the idea that the primary processes in iso...
متن کاملCircular dichroism spectra and the molecular arrangement of bacteriochlorophylls in the reaction centers of photosynthetic bacteria.
Chromatophores, or membrane fragments, prepared from photosynthetic bacteria exhibit a variety of properties which demonstrate that they are able to carry out the quantum conversion steps characteristic of the intact bacterial cells.", 2 The pigment molecules consist of two distinct functional types: an antenna, which includes over 90 per cent of the bacteriochlorophyll molecules, and a smaller...
متن کامل