Functional and mutational analysis of the light-harvesting chlorophyll a/b protein of thylakoid membranes.

The precursor for a Lemna light-harvesting chlorophyll a/b protein (pLHCP) has been synthesized in vitro from a single member of the nuclear LHCP multigene family. We report the sequence of this gene. When incubated with Lemna chloroplasts, the pLHCP is imported and processed into several polypeptides, and the mature form is assembled into the light-harvesting complex of photosystem II (LHC II). The accumulation of the processed LHCP is enhanced by the addition to the chloroplasts of a precursor and a co-factor for chlorophyll biosynthesis. Using a model for the arrangement of the mature polypeptide in the thylakoid membrane as a guide, we have created mutations that lie within the mature coding region. We have studied the processing, the integration into thylakoid membranes, and the assembly into light-harvesting complexes of six of these deletions. Four different mutant LHCPs are found as processed proteins in the thylakoid membrane, but only one appears to have an orientation in the membrane that is similar to that of the wild type. No mutant LHCP appears in LHC II. The other two mutant LHCPs cannot be detected within the chloroplasts. We conclude that stable complex formation is not required for the processing and insertion of altered LHCPs into the thylakoid membrane. We discuss the results in light of our model.

Download Full-text

Fucoxanthin-Chlorophyll a/c Light-Harvesting Complexes of Laminaria saccharina: Partial Amino Acid Sequences and Arrangement in Thylakoid Membranes

Biochemistry ◽

10.1021/bi00177a004 ◽

1994 ◽

Vol 33 (11) ◽

pp. 3165-3170 ◽

Cited By ~ 18

Author(s):

Dominique Douady ◽

Bernard Rousseau ◽

Lise Caron

Keyword(s):

Amino Acid ◽

Chlorophyll A ◽

Light Harvesting ◽

Thylakoid Membranes ◽

Amino Acid Sequences ◽

Light Harvesting Complexes ◽

Laminaria Saccharina

Download Full-text

High-Resolution electron crystallography of the light-harvesting chlorophyll-a/b protein complex from chloroplast membranes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100181816 ◽

1990 ◽

Vol 48 (1) ◽

pp. 610-610

Author(s):

Werner Kühlbrandt ◽

Da Neng Wang ◽

K.H. Downing

Keyword(s):

High Resolution ◽

Electron Diffraction ◽

Chlorophyll A ◽

Protein Complex ◽

Structural Integrity ◽

Light Harvesting ◽

Lhc Ii ◽

Diffraction Patterns ◽

Difference Fourier ◽

2D Crystals

The light-harvesting chlorophyll-a/b protein complex (LHC-II) is the most abundant membrane protein in the chloroplasts of green plants where it functions as a molecular antenna of solar energy for photosynthesis. We have grown two-dimensional (2d) crystals of the purified, detergent-solubilized LHC-II . The crystals which measured 5 to 10 μm in diameter were stabilized for electron microscopy by washing with a 0.5% solution of tannin. Electron diffraction patterns of untilted 2d crystals cooled to 130 K showed sharp spots to 3.1 Å resolution. Spot-scan images of 2d crystals were recorded at 160 K with the Berkeley microscope . Images of untilted crystals were processed, using the unbending procedure by Henderson et al . A projection map of the complex at 3.7Å resolution was generated from electron diffraction amplitudes and high-resolution phases obtained by image processing .A difference Fourier analysis with the same image phases and electron diffraction amplitudes recorded of frozen, hydrated specimens showed no significant differences in the 3.7Å projection map. Our tannin treatment therefore does not affect the structural integrity of the complex.

Download Full-text

Studies on the Herbicide Binding Site in Isolated Photosystem II Core Complexes from a Flat-Bed Isoelectrofocusing Method

Zeitschrift für Naturforschung C ◽

10.1515/znc-1990-0510 ◽

1990 ◽

Vol 45 (5) ◽

pp. 366-372 ◽

Cited By ~ 6

Author(s):

M. T. Giardi ◽

J. Barber ◽

M. C. Giardina ◽

R. Bassi

Keyword(s):

Light Harvesting ◽

Resistant Mutant ◽

Separation Procedure ◽

Chlorophyll B ◽

Core Complex ◽

Light Harvesting Complexes ◽

Lhc Ii ◽

Ps Ii ◽

Α Subunit ◽

Ps Ii Core

Abstract Isoelectrofocusing has been used to separate various chlorophyll-protein complexes of photosystem two (PS II). Light-harvesting complexes containing chlorophyll a and chlorophyll b (LHC II) were located in bands having p/s in the region of 4.5. At slightly higher pH other light-harvesting complexes containing little or no chlorophyll b were found. In the most basic region of the isoelectrofocusing gel, were located PS II core complexes characterized by containing the proteins of CP47, CP43, D 1, D 2 and α-subunit of cytochrome b559. The number of PS II core bands depended on the particular conditions employed for the separation procedure and in some cases were contaminated by CP 29. It is suggested that this heterogeneity resulting from different protonation states of the PS II. The least-acidic PS II core complex (pI 5.5) was found to bind the herbicides atrazine, diuron and dinoseb. In contrast, a PS II core complex with a p / of 4.9 bound only diuron. Its inability to bind atrazine was shown to be due to the low pH but no such explanation could be found for dinoseb. When atrazine-resistant mutant Senecio vulgaris was used, no binding of radioactive atra zine was observed with the PS II cores having a p i of 5.5. It is therefore suggested that the normal atrazine binding observed with PS II cores involves the high affinity site detected with intact membranes. With the PS II cores, however, this site has a reduced affinity probably due to structural modification in the D 1-polypeptide resulting from the isolation procedures.

Download Full-text

Optimization of light harvesting and photoprotection: molecular mechanisms and physiological consequences

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2012.0069 ◽

2012 ◽

Vol 367 (1608) ◽

pp. 3455-3465 ◽

Cited By ~ 76

Author(s):

Peter Horton

Keyword(s):

Protein Interactions ◽

Thylakoid Membrane ◽

Molecular Mechanisms ◽

Light Harvesting ◽

Protein Complexes ◽

Efficient Energy Transfer ◽

Light Harvesting Complexes ◽

Functional Flexibility ◽

Jan Anderson ◽

Repulsive Forces

The distinctive lateral organization of the protein complexes in the thylakoid membrane investigated by Jan Anderson and co-workers is dependent on the balance of various attractive and repulsive forces. Modulation of these forces allows critical physiological regulation of photosynthesis that provides efficient light-harvesting in limiting light but dissipation of excess potentially damaging radiation in saturating light. The light-harvesting complexes (LHCII) are central to this regulation, which is achieved by phosphorylation of stromal residues, protonation on the lumen surface and de-epoxidation of bound violaxanthin. The functional flexibility of LHCII derives from a remarkable pigment composition and configuration that not only allow efficient absorption of light and efficient energy transfer either to photosystem II or photosystem I core complexes, but through subtle configurational changes can also exhibit highly efficient dissipative reactions involving chlorophyll–xanthophyll and/or chlorophyll–chlorophyll interactions. These changes in function are determined at a macroscopic level by alterations in protein–protein interactions in the thylakoid membrane. The capacity and dynamics of this regulation are tuned to different physiological scenarios by the exact protein and pigment content of the light-harvesting system. Here, the molecular mechanisms involved will be reviewed, and the optimization of the light-harvesting system in different environmental conditions described.

Download Full-text