Topography of thylakoid membranes: In situ localization of photosystems I and II. [Porphyridium cruentum]

Conference · Wed May 01 04:00:00 EDT 1991 · Plant Physiology, Supplement; (United States)

OSTI ID:5401938

Gantt, E; Mustardy, L; Cunningham, Jr, F X ^[1]

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1. Univ. of Maryland, College Park (United States)

The organization of the photosynthetic membrane structure is being studied in the red alga Porphyridium cruentum. Excitation energy transfer between the photosystems, which occurs readily in red algae and cyanobacteria, requires a close spatial relationship between the photosystems. The authors initial efforts have focused on the in situ labelling of PSI and PSII, two of four major protein complexes in thylakoids. Stoichiometries of PSI and PSII in P. cruentum are readily affected by light spectral quality. Cultures grown under continuous red light contain nearly five times as many A{sub A}'s per P{sub 700} as cells grown under green light. Thylakoids were isolated from cells grown under red or green light, and rinsed exhaustively to remove stromal proteins and phycobilisomes. These membranes were spread on electron microscope grids and immunolabelled with affinity-purified IgG antibodies to PSI and PSII. Gold particles were directly coupled to the antibodies of PSI (10 nm Au) and PSII (15nm Au). The labelling results are consistent with the Q{sub A} and P{sub 700} determinations. The density of PSII is greater in membranes from red light cells relative to green light cells, while the PSI density is greater in green light cells. The photosystems appear to be uniformly distributed over the thylakoid membranes. Double labelling experiments indicate that PSI and PSII can occur in close proximity with a distance of less than 20 nm. Such proximity increases the possibility of excitation energy transfer between PSI and PSII.

• OSTI ID: 5401938
• Report Number(s): CONF-9107184--
• Conference Information: Journal Name: Plant Physiology, Supplement; (United States) Journal Volume: 96:1
• Country of Publication: United States
• Language: English

Related Subjects

551000* -- Physiological Systems
59 BASIC BIOLOGICAL SCIENCES
ALGAE
BIOASSAY
CELL CULTURES
CHARGE EXCHANGE
IMMUNOASSAY
MEMBRANE PROTEINS
MEMBRANES
ORGANIC COMPOUNDS
PHOTOSYNTHETIC MEMBRANES
PHYSIOLOGY
PLANTS
PROTEINS
THYLAKOID MEMBRANE PROTEINS