Protein identification of purified particles isolated from spinach thylakoids by deoxycholate electrophoresis

Abstract

Three thylakoid complexes were isolated by deoxycholate preparative electrophoresis. The protein composition of each fraction was analyzed by SDS analytical electrophoresis. No protein of the PS 1 enriched fraction (fraction 1) was found in the PS 2 enriched fraction (fraction 2) and inversely. The antenna complex (fraction 3) did not have any contamination by proteins of fraction 1 or fraction 2. Fraction 1 was mainly composed of the CP1, the reaction center complex of the PS1, and by low molecular weight proteins, previously found in other PS 1 preparations. Tentative assignments of these proteins are presented; among them are iron sulfur proteins. After analytical SDS electrophoresis of fraction 2, the reaction center complex was dissociated. Nevertheless three proteins of 50 kD, 42 kD and 35 kD were assigned to this complex. Fraction 2 contained also the three cytochromes of the thylakoid membranes: cyt f, cyt b6, cyt b559. Fraction 3 was exclusively composed of one protein pigment complex, CP2.

Partial characterization of a minor chlorophyll-protein found in primary thylakoids of intermittently illuminated maize

“…Polypeptides like that are generally related to photosystem II [11,25]. Recently polypeptides of similar apparent molecular weights were shown in photosystem II reaction centre complexes containing only several distinct polypeptides [1,29]. Our results with mesophyll and bundle sheath thylakoids also show some parallel between the occurrence of the new CP and CP a ( Table 1), but determination of its function and structural relations need further investigation.…”

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

“…For analysis of the polypeptides in the pigment-protein complexes by SDS-PAGE [1], the sedimented complexes were resuspended in 2% SDS, 50mM DTT, and 50mM Tris-HC1, pH 8 and heated at 100°C for 30s. For comparison, some complexes were first delipidated by making a concentrated extract to 80% with acetone and incubating at 4 °C for 1 h. Then, with the extract in a glass centrifuge tube, ethyl ether was added dropwise until two phases developed.…”

A single step separation of PS 1, PS 2 and chlorophyll-antenna particles from spinach chloroplasts

“…By pigment analysis ( Table 2) we found 1.2 for the chlorophyll a/chlorophyll b ratio, this ratio being characteristic of the antenna complex [23]. The low absorption in the UV region arising from aromatic amino acid residues and the low amount of protein (2 mg/mg chl) suggest a protein purification of the complex as demonstrated by SDS PAGE [2]. Fraction 1 had an absorption spectrum typical of a PS 1 preparation.…”

“…It would be very interesting to know whether these additional proteins are acceptors, still able to reduce PS 1, acceptors that are missing in CPI. Preliminary results of this study are presented in the accompanying paper [2]. The absorption spectrum of the PS 2 enriched particle (fraction 2), had its maximum in the red at 674 nm.…”