Document Detail

Light-dependent chlorophyll a biosynthesis upon chlL deletion in wild-type and photosystem I-less strains of the cyanobacterium Synechocystis sp. PCC 6803.
MedLine Citation:
PMID:  8555457     Owner:  NLM     Status:  MEDLINE    
Part of the chlL gene encoding a component involved in light-independent protochlorophyllide reduction was deleted in wild type and in a photosystem I-less strain of Synechocystis sp. PCC 6803. In resulting mutants, chlorophyll biosynthesis was fully light-dependent. When these mutants were propagated under light-activated heterotrophic growth conditions (in darkness except for 15 min of weak light a day) for several weeks, essentially no chlorophyll was detectable but protochlorophyllide accumulated. Upon return of the chlL- mutant cultures to continuous light, within the first 6 h chlorophyll was synthesized at the expense of protochlorophyllide at a rate independent of the presence of photosystem I. Chlorophyll biosynthesized during this time gave rise to a 685 nm fluorescence emission peak at 77 K in intact cells. This peak most likely originates from a component different from those known to be directly associated with photosystems II and I. Development of 695 and 725 nm peaks (indicative of intact photosystem II and photosystem I, respectively) required longer exposures to light. After 6 h of greening, the rate of chlorophyll synthesis slowed as protochlorophyllide was depleted. In the chlL- strain, greening occurred at the same rate at two different light intensities (5 and 50 microE m-2 s-1), indicating that also at low light intensity the amount of light is not rate-limiting for protochlorophyllide reduction. Thus, in this system the rate of chlorophyll biosynthesis is limited neither by biosynthesis of photosystems nor by the light-dependent protochlorophyllide reduction. We suggest the presence of a chlorophyll-binding 'chelator' protein (with 77 K fluorescence emission at 685 nm) that binds newly synthesized chlorophyll and that provides chlorophyll for newly synthesized photosynthetic reaction centers and antennae.
Q Wu; W F Vermaas
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Plant molecular biology     Volume:  29     ISSN:  0167-4412     ISO Abbreviation:  Plant Mol. Biol.     Publication Date:  1995 Dec 
Date Detail:
Created Date:  1996-02-26     Completed Date:  1996-02-26     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9106343     Medline TA:  Plant Mol Biol     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  933-45     Citation Subset:  IM    
Department of Botany, Arizona State University, Tempe 85287-1601, USA.
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MeSH Terms
Bacterial Proteins / genetics*
Base Sequence
Chlorophyll / biosynthesis*
Cyanobacteria / genetics*,  growth & development,  metabolism
DNA Primers
DNA, Bacterial
Molecular Sequence Data
Photosynthetic Reaction Center Complex Proteins / genetics*
Pigments, Biological / metabolism
Sequence Deletion
Spectrometry, Fluorescence
Reg. No./Substance:
0/Bacterial Proteins; 0/DNA Primers; 0/DNA, Bacterial; 0/Photosynthetic Reaction Center Complex Proteins; 0/Pigments, Biological; 0/Proteins; 0/chlL protein, bacteria; 1406-65-1/Chlorophyll; 479-61-8/chlorophyll a

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