Evidence for a light-harvesting chlorophyll a-protein complex in a chlorophyll b-less barley mutant

Abstract

Chloroplasts of a chlorophyll (Chl) b-less barley mutant were solubilized with digitonin and fractionated by polyacrylamide gel electrophoresis with sodium deoxycholate in the running buffer. By this procedure, in contrast to using sodium dodecylsulfate (SDS) for solubilization, a Chl a-protein analogous to the major light-harvesting Chl a-b protein complex from wildtype chloroplasts was recovered. This mutant Chl a-protein comprises about fifty percent of the total Chl a, and is very similar in carotenoid, amino acid, protein and polypeptide composition to the major wildtype antenna Chl a-b protein. The only major differences we have found is its instability in the presence of SDS and sensitivity to protease action. Even with deoxycholate, the mutant Chl a complex often dissociates during electrophoresis into two green bands. The lack of Chl b appears to affect the normal organization of Chl a and protein in such a way as to render the complex more unstable.

Regulation of LHCa‐Polypeptide‐Biosynthesis in the Phototrophic Green Alga Chlamydobotrys stellata*

“…Our observation on the very low Chl b-content of LHCa is paralleled by reports on other only Chla-containing LHCpolypeptides, e.g. Chl b-less mutants (Duranton and Brown, 1987;White and Green, 1987a). Evidently light-harvesting chlorophyll proteins can exist in the absence of Chl b or at very low Chl b contents, but the lack of Chl b destabilizes the complex organization White and Green, 1987b), and can even prevent the incorporation of the LHC-precursors into the thylakoid membranes (Bellemare et al, 1982;Cunningham and Schiff, 1986;Michel et al, 1983;White and Green, 1987b).…”

Functional Organization of Chlorophyll a and Carotenoids in the Alga, Nannochloropsis salina

“…The position in the gel after electrophoresis, absorption spectrum, and pigment content of the algal PSII complex are all properties similar to PSII from higher plants; but, like PSI, its relative proportion seems to be lower (7% compared to 15% for spinach, Table I (9), probably because these pigment-proteins without Chl b are extremely labile and more susceptible to both protease and detergent action (12). The procedure used to isolate a Chl a antenna complex from the Chlorina-f2 barley mutant was the same as that applied here to N. salina, and the gel pattern for the fastest running green bands (LHCII and FP) were similar ( Table I).…”