ISSN:
1573-5028
Keywords:
D1 polypeptide
;
photoinhibition
;
photosystem II
;
protein turnover
;
site-specific mutants
;
Synechocystis 6803
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The degradation rate of the D1 polypeptide was measured in threeSynechocystis PCC 6803 mutantsin vivo. Mutations were introduced into a putative cleavage area of the D1 polypeptide (QEEET motif) and into the PEST-like area. PEST sequences are often found in proteins with a high turnover rate. The QEEET-motif mutants are CA1 [Δ(E242-E244);Q241H] and E243K, and the third mutation, E229D, was directed to the PEST-like area. During high-light illumination (1500 μmol photons m-2s-1) that induced photoinhibition of photosystem II (PSII), the half-life time of the D1 polypeptide in mutant E229D (t 1/2=35 min) was about twice as long as in AR (control strain) cells (t 1/2=19 min). In growth light (40 μmol photons m-2s-1), the degradation rate of the D1 polypeptide in E229D and AR strains was the same (t 1/2≈5 h). In growth light the D1 polypeptide was degraded faster in both QEEET-motif mutants than in the AR strain, but in photoinhibitory light the degradation rates were similar. According to these results, the highly conservative QEEET motif as such is not required for the proteolytic cut of the D1 polypeptide, but it does affect the rate of degradation. No simple correlation existed between the degradation rate of the D1 polypeptide and the susceptibility of PSII to photoinhibition in mutant and AR cells under our experimental conditions.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00043879
