Chlorophyll antenna proteins of photosystem I: topology, synthesis, and regulation of the 20-kDa subunit of Chlamydomonas light-harvesting complex of photosystem I

Journal Article · Fri May 01 00:00:00 EDT 1987 · Arch. Biochem. Biophys.; (United States)

DOI:https://doi.org/10.1016/0003-9861(87)90117-2· OSTI ID:6501780

Herrin, D L; Plumley, F G; Ikeuchi, M; Michaels, A S; Schmidt, G W

The light-harvesting complex of photosystem I (LHCI) was isolated from wild-type cells of Chlamydomonas reinhardtii; the Chl a/b-protein complex contains four major polypeptides of approximately 27, 26, 24, and 20 kDa (polypeptides 14, 15, 17.2, and 22, respectively, in the nomenclature for Chlamydomonas thylakoid proteins). Antiserum against the 20-kDa subunit of LHCI was prepared and used to determine the membrane topology, subcellular site of synthesis, and cell-cycle regulation of this polypeptide. The results indicate that the 20-kDa subunit as well as the other major LHCI polypeptides are integral membrane proteins. Moreover, protease digestion experiments reveal that the 20-kDa polypeptide is completely protected by the membrane bilayer but the 27- and 26-kDa LHCI polypeptides are exposed at the membrane surface. In vivo synthesis of the 20-kDa polypeptide is sensitive to cycloheximide but not to chloramphenicol; the form of the polypeptide recovered from in vitro translations of polyadenylated RNA is approximately 24 kDa, 4 kDa larger than the mature polypeptide. It is concluded that this LHCI polypeptide is nuclear encoded and synthesized in the cytoplasm as a higher molecular weight precursor. Synthesis of the 20-kDa polypeptide is restricted to the light period in light-dark synchronized cells. Translatable mRNA for this polypeptide accumulates during the light but levels are dramatically reduced during the dark period. Thus, synthesis of the 20-kDa subunit of LHCI appears to be transcriptionally regulated during the cell cycle.

• Research Organization: Univ. of Georgia, Athens
• OSTI ID: 6501780
• Journal Information: Arch. Biochem. Biophys.; (United States), Vol. 2
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
PHOTOSYNTHETIC REACTION CENTERS
PROTEIN STRUCTURE
BIOSYNTHESIS
CELL CYCLE
CHLAMYDOMONAS
CHLORAMPHENICOL
CHLOROPHYLL
CYCLOHEXIMIDE
CYTOPLASM
GENE REGULATION
IMMUNOASSAY
MOLECULAR WEIGHT
PEPTIDE HYDROLASES
PHOTOSYNTHESIS
TRANSCRIPTION
ALGAE
ANTI-INFECTIVE AGENTS
ANTIBIOTICS
CARBOXYLIC ACIDS
CELL CONSTITUENTS
CHEMICAL REACTIONS
DRUGS
ENZYMES
FUNGICIDES
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROLASES
MICROORGANISMS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PESTICIDES
PHOTOCHEMICAL REACTIONS
PHYTOCHROMES
PIGMENTS
PLANTS
PORPHYRINS
PROTEINS
SYNTHESIS
UNICELLULAR ALGAE
550200* - Biochemistry
550400 - Genetics