Chlorophyll-protein complexes from thylakoids of a mutant barley lacking chlorophyll b.

Abstract

Modifications of the type and concentration of detergents and buffers used for thylakoid extraction and gel electrophoresis have provided improved resolution of chlorophyll‐protein complexes in mutant barley which lacks chlorophyll b. The use of sodium deoxycholate in the gels and in the solubilization of thylakoids reduced the amount of free chlorophyll significantly. Three chlorophyll‐a–protein complexes were resolved from mutant barley; two of these (CP1a and CP1) represent the reaction centre complex of photosystem 1, while the third complex, CPa, is the presumed reaction centre of photosystem 2. The fluorescence emission band of mutant barley complex CPa at 684 nm and the low fluorescence yield are consistent with expected characteristics of a reaction centre complex of photosystem 2. More chlorophyll (60 %) is associated with the reaction centre complex of photosystem 1 than with the presumed reaction centre complex of photosystem 2 (30%), and these amounts are double those found in the corresponding complexes of normal barley. It is proposed that the smaller photosynthetic unit of mutant barley thylakoids has twice as much chlorophyll a in photosystem 1 as in photosystem 2, and this chlorophyll is associated only with the two reaction centre complexes which are in direct contact. The sodium deoxycholate method may be useful for the resolution of pigment complexes from other thylakoids with inherently fragile photosystems.