Luminescence Study of PS 1 Pigment-Protein Complexes Isolated from the Cyanobacterium Plectonema Boryanum

Abstract

We have recently isolated and characterised the PS 1 pigment-protein complexes (PPCs) from the cyanobacterium Plectonema boryanum (Hladík and Sofrová (1981)). Isolation procedure — extraction of thylakoid membranes by Triton X-100, followed by the chromatography on DEAE cellulose column — yields two fractions; first containing complex of M_r 260 000 (denoted as PPC III), the second containing complex of M_r 118 000 (denoted as PPC II). It was shown (Hladík et al. (1982)) that the quarternary structure of the PPC III protein is — at least partly — conserved : this complex was found to be the oligomer of PPC II. We have proved that specificaly oriented carotenoids (characterised by strong positive circular dichroism bands at 480 and 505 nm) mediate the substantial part of the interactions between the pigment-protein subunits. The presence of protein-fixed, chiraly arranged carotenoids in PPCs seems to be a more general property of these systems: they were found in bacteria (Cogdell et al. (1976)) and also in PPCs from higher plants (Schubin et al. (1981)). The aim of our work was to study the functional consequences of this structural feature of PS 1 complex.