Adhesion between liposomes mediated by the chlorophyll a/b light-harvesting complex isolated from chloroplast membranes.
Open Access
- 1 January 1980
- journal article
- research article
- Published by Rockefeller University Press in The Journal of cell biology
- Vol. 84 (1), 40-56
- https://doi.org/10.1083/jcb.84.1.40
Abstract
A highly purified chlorophyll a/b light-harvesting complex (chl a/b LHC; chl a/b ratio 1.2) was obtained from Triton-solubilized chloroplast membranes of pea and barley according to the method of Burke et al. (1978, Arch. Biochem. Biophys. 187: 252--263). Gel electrophoresis of the cation-precipitated chl a/b LHC from peas reveals the presence of four polypeptides in the 23- to 28-kdalton size range. Three of these peptides appear to be identical to those derived from re-electrophoresed CPII and CPII* bands. In freeze-fracture replicas, the cation-precipitated chl a/b LHC appears as a semicrystalline aggregate of membranous sheets containing closely spaced granules. Upon removal of the cations by dialysis, the aggregates break up into their constituent membranous sheets without changing their granular substructure. These membranous sheets can be resolubilized in 1.5% Triton X-100, and the chl a/b LHC particles then reconstituted into soybean lecithin liposomes. Freeze-fracture micrographs of the reconstituted chl a/b LHC vesicles suspended in a low salt medium reveal randomly dispersed approximately 80-A particles on both concave and convex fracture faces as well as some crystalline particle arrays, presumably resulting from incompletely solubilized fragments of the membranous sheets. Based on the approximately 80-A diameter of the particles, and on the assumption that one freeze-fracture particle represents the structural unit of one chl a/b LHC aggregate, a theoretical mol wt of approximately 200 kdalton has been calculated for the chl a/b LHC. Deep-etching and negative-staining techniques reveal that the chl a/b LHC particles are also exposed on the surface of the bilayer membranes. Addition of greater than or equal to 2 mM MgCl2 or greater than or equal to 60 mM NaCl to the reconstituted vesicles leads to their aggregation and, with divalent cations, to the formation of extensive membrane stacks. At the same time, the chl a/b LHC particles become clustered into the adhering membrane regions. Under these conditions the particles in adjacent membranes usually become precisely aligned. Evidence is presented to aupport the hypothesis that adhesion between the chl a/b LHC particles is mediated by hydrophobic interactions, and that the cations are needed to neutralize surface charges on the particles.This publication has 21 references indexed in Scilit:
- Resolution of the light-harvesting chlorophyll ab-protein of Vicia faba chloroplasts into two different chlorophyll-protein complexesBiochimica et Biophysica Acta (BBA) - Bioenergetics, 1979
- Immunochemical studies of thylakoid membrane polypeptides from spinach and Chlamydomonas reinhardtii. A modified procedure for crossed immunoelectrophoresis of dodecyl sulfate.protein complexes.Journal of Biological Chemistry, 1979
- Effects of Ions and Gravity Forces on the Supramolecular Organization and Excitation Energy Distribution in Chloroplast MembranesPublished by Wiley ,1979
- Energy Transfer and its Dependence on Membrane PropertiesPublished by Wiley ,1979
- Involvement of the light-harvesting complex in cation regulation of excitation energy distribution in chloroplastsArchives of Biochemistry and Biophysics, 1978
- Characterization of three new chlorophyll-protein complexesBiochemical and Biophysical Research Communications, 1978
- Freeze‐Fracture Appearance and Disposition of Band 3 Protein from the Human Erythrocyte Membrane in Lipid VesiclesEuropean Journal of Biochemistry, 1978
- Analysis of the thylakoid outer surface. Coupling factor is limited to unstacked membrane regions.The Journal of cell biology, 1976
- The molecular organization of chloroplast thylakoidsBiochimica et Biophysica Acta (BBA) - Reviews on Bioenergetics, 1975
- Cleavage of Structural Proteins during the Assembly of the Head of Bacteriophage T4Nature, 1970