Subunit Interactions and Protein Stability in the Cyanobacterial Light-Harvesting Proteins

Publication Status is "Submitted" Or "In Press: 
LDEO Publication: 
Publication Type: 
Year of Publication: 
1995
Editor: 
Journal Title: 
Journal of Bacteriology
Journal Date: 
Dec
Place Published: 
Tertiary Title: 
Volume: 
177
Issue: 
23
Pages: 
6798-6803
Section / Start page: 
Publisher: 
ISBN Number: 
0021-9193
ISSN Number: 
Edition: 
Short Title: 
Accession Number: 
ISI:A1995TG22400015
LDEO Publication Number: 
Call Number: 
Abstract: 

Strain 4R is a phycocyanin-minus mutant of the unicellular cyanobacterium Synechocystis sp, strain 6803. Although it lacks the light-harvesting protein phycocyanin, 4R has normal levels of phycocyanin (cpc) transcripts. Sequence analysis of the cpcB gene encoding the phycocyanin beta subunit shows an insertion mutation in 4R that causes early termination of translation. Other work has shown that the phycocyanin alpha subunit and the linker proteins encoded on the cpc transcripts are all functional in 4R, yet the defective phycocyanin beta subunit results in the complete absence of the alpha subunit and the linkers. Phycocyanin-minus mutants were constructed in a wild-type background by interruption of cpcB and cpcA with an antibiotic resistance gene and were compared with the 4R strain. Immunoblot analysis of the mutants demonstrated that interruption of one subunit was accompanied by a complete absence of the unassembled partner subunit. Phycocyanin assembly begins with the formation of the alpha beta heterodimer (the monomer) and continues through higher-order trimeric and hexameric aggregates th;tt associate with linker proteins to form the phycobilisome rods. The results in this paper indicate that monomer formation is a critical stage in the biliprotein assembly pathway and that unassembled subunits are subject to stringent controls that prevent their appearance in vivo.

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Tg224Times Cited:10Cited References Count:43

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