Chlorophyll-Protein Complexes from Euglena gracilis and Mutants Deficient in Chlorophyll b

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Abstract
The use of n-octyl-.beta.-D-glucopyranoside along with sodium dodecyl sulfate improves the retention of chlorophyll (Chl) by chlorophyll-protein complexes (CPs) prepared from thylakoids of Euglena gracilis Klebs var bacillaris Cori and yields several additional complexes. Thylakoids from wild-type (WT) cells, solubilized in these detergents and subjected to polyacrylamide gel electrophoresis at 0.degree. C, yield the following CPs in order of relative molecular weight, containing the pigments shown in parentheses with their respective molar ratios where determined: CP Ia (Chl a, diadinoxanthin and .beta.-carotene; 100:12:5); CP I (Chl a and .beta.-carotene; 100:6-12); CPx (Chl and carotenoids); LHCP2(light-harvesting CP oligomer) (Chl a, Chl b, diadinoxanthin and neoxanthin; 12:4:3:1); CPy (Chl a, diadinoxanthin and .beta.-carotene; 100:14:8); CPa (Chl a and .beta.-carotene; 100:18-25) and LHCP (monomer) (Chl a, Chl b, diadinoxanthin and neoxanthin; 12:6:4:1). The LHCP complexes retain up to 40% of the total Chl and 80% of the Chl b in the thylakoids. CP Ia contains only a trace of Chl b (Chl a/b [mol/mol] = 62). The lower amount of Chl b in Euglena (about 10% of Chl a + b) compared to higher plants (about 30% of Chl a + b) is probably a consequence of the lower Chl b (relative to Chl a) in the LHCPs of Euglena rather than of fewer LHCPs being present. G1BU, Gr1BSL, and O4BSL, mutants of bacillaris low in Chl b (1-2% of Chl a + b), lack the CP Ia, LHCP, and LHCP2 found in wild-type (WT); G1 and O4 also lack CPy. The mutants contain reduced amounts of Chl a (two-thirds of WT in Gr1 ane one-third in G1 and O4) and neoxanthin (20-40% of WT) but retain levels of .beta.-carotene and diadinoxanthin close to those in cells of WT. The CPs remaining in the mutants have pigment compositions very similar to their counterparts from WT.