In vitro synthesis of photosynthetic membranes: I. Development of photosystem I activity and cyclic photophosphorylation

Daniell, H.; Ramanujam, P.; Krishnan, M.; Gnanam, A.; Rebeiz, C.A.

Biochemical and Biophysical Research Communications 111(2): 740-749


ISSN/ISBN: 0006-291X
PMID: 6838579
Accession: 005652519

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The 1st successful in vitro synthesis of functional photosynthetic phosphorylating membrane is reported. Etioplasts, highly enriched in cytoplasmic and plastid proteins, isolated from etiolated cucumber cotyledons pretreated with kinetin and GA and illuminated in a cofactor fortified medium showed the begining of chlorophyll (Chl) synthesis immediately after illumination from exogenous .delta.-aminolevulinic acid, while photosystem I (PS I) activity commenced 15 min after the onset of illumination. When cotyledons pretreated with kinetin and GA were illuminated directly, there was a lag phase of 30 min before the commencement of Chl synthesis and PS I activity developed after 1 h of illumination. In plastids developed in vivo and in vitro, the electron flow from dichlorophenolindophenol to methylviologen was coupled to phosphorylation as observed by an increase in the electron transport rate on the addition of uncouplers. Analysis of polypeptide profiles of the greening plastids in vitro showed the disappearance of many higher MW proteins during greening. Polypeptides of MW 32, 20.5, 19.5 K absent in etioplasts appeared as distinct bands after 4 h of greening in vitro.