Plant Physiol, November 2000, Vol. 124, pp. 1403-1412
The Carboxyl-Terminal Extension of the Precursor D1 Protein of
Photosystem II Is Required for Optimal Photosynthetic Performance of
the Cyanobacterium Synechocystis sp. PCC
68031
Natalia B.
Ivleva,
Sergey V.
Shestakov, and
Himadri B.
Pakrasi*
Department of Biology, Box 1137, Washington University, St. Louis,
Missouri 63130 (N.B.I., H.B.P.); and Department of Genetics, Moscow
State University, Moscow 119899, Russia (N.B.I., S.V.S.)
The D1 protein is an integral component of the photosystem II
reaction center complex. In the cyanobacterium
Synechocystis sp. PCC 6803, D1 is synthesized with a
short 16-amino acids-long carboxyl-terminal extension. Removal of this
extension is necessary to form active oxygen-evolving photosystem II
centers. Our earlier studies have shown that this extension is cleaved
by CtpA, a specific carboxyl-terminal processing protease. The amino
acid sequence of the carboxyl-terminal extension is conserved among D1
proteins from different organisms, although at a level lower than that of the mature protein. In the present study we have analyzed a mutant
strain of Synechocystis sp. PCC 6803 with a duplicated extension, and a second mutant that lacks the extension, to investigate the effects of these alterations on the function of the D1 protein in
vivo. No significant difference in the growth rates, photosynthetic pigment composition, fluorescence induction, and oxygen evolution rates
was observed between the mutants and the control strain. However, using
long-term mixed culture growth analysis, we detected significant
decreases in the fitness of these mutant strains. The presented data
demonstrate that the carboxyl-terminal extension of the precursor D1
protein is required for optimal photosynthetic performance.
1
This work was supported by grants from National
Institutes of Health (GM 45797 to H.B.P.) and from the International
Human Frontier Science Program (to H.B.P. and S.V.S.). N.B.I. was
partially supported by a training grant from the Monsanto Company to
the Plant Biology Program at Washington University.
*
Corresponding author; e-mail Pakrasi{at}biology.wustl.edu; fax
314-935-6803.
© 2000 American Society of Plant Physiologists
