Chlorophyll-proteins of two photosystem I preparations from maize

Abstract

Two photosystem I (PSI) preparations were purified by non-denaturing SDS-PAGE or sucrose gradient ultracentrifugation and examined as to their chlorophyll-protein composition. In both preparations a minimum of two chlorophyll-proteins can be distinguished in addition to the 110 kD P-700 Chlo-P 1 complex. One (LHCI-730) is a chlorophyll-protein (Mr 40 kD) having a high chlorophyll a/b ratio, and a major 77 K fluorescence peak at 730 nm. It consists of three polypeptides with apparent molecular weights of 21, 22.5 and 24 kD. Another chlorophyll-protein (LHCI-680) with a lower molecular weight (Mr 25 kD) fluoresces at 77 K with a maximum at 680 nm. This chlorophyll-protein has a high chlorophyll b content and two constituent polypeptides of 20 and 25 kD. Absorption, 77 K fluorescence and circular dichroism spectra of the PSI related chlorophyll-proteins are presented and compared with those of photosystem II chlorophyll-proteins from maize thylakoids. We propose a model for energy transfer in the photosystem I reaction centre with the following sequence: LHCI-730 ~ LHCI-680ChL-P 1. LHCI-680 acts as a connecting antenna which can also transfer energy from ChL/b-P2. This model was used to interpret the 77 K fluorescence emission from two barley mutants.

The role of the light harvesting complex and photosystem II in thylakoid stacking in thechlorina-f2 barley mutant

“…The Chl~-P 1" complex from chlorina-f2 differed from that of wild-type due to the lack of the antennae complexes LHCI-680 and LHCI-730, and thus corresponded to the PSI-65 particle of maize and pea (4,19), consisting of Chlo-Pl and low molecular weight po[ypeptides. When thylakoids isolated from chlorina-f2 plants grown under continuous illumination were examined, an additional band (x) appeared with a mobility similar to Chlo/~,-P2 (Figure 9a).…”

“…Separation of chlorphyll-proteins by nondenaturing SDS-PAGE was carried out at 4 ~ as described in (3,4). Thylakoids were solubilized with SDS (SDS:Chl = 10:1 w/w) or with 13-octyl glucoside (octyl glucoside:Chl = 30:1 w/w for wild type thylakoids and 40:1 for chlorina-f2 thylakoids).…”

“…Thylakoids were solubilized with SDS (SDS:Chl = 10:1 w/w) or with 13-octyl glucoside (octyl glucoside:Chl = 30:1 w/w for wild type thylakoids and 40:1 for chlorina-f2 thylakoids). Denaturing SDS-PAGE in the presence of 6 M-urea was run with the buffer system described in (4) in an apparatus with cooling on both sides of 30 • 30 cm glass plates. The gel contained a 10 to 20% linear acrylamide gradient.…”

Differential expression of LHCII genes in mesophyll and bundle sheath cells of maize

“…Non-denaturing and SDS-urea polyacrylamide gel electrophoresis were performed as described in (4). PSII electron transport measurements were made with an Aminco DW-2a spectrophotometer using DPC and DCPIP as electron donor and acceptor (2).…”

Probing in vitro translation products with monoclonal antibodies to chlorophylla/b-binding proteins of barley thylakoids

“…In barley photosystem I (PSI) preparations isolated by Triton X-100 solubilisation of thylakoids yield upon sucrose gradient centrifugation two chlorophyll a/b-binding proteins. They are identified by their low-temperature fluorescence emission spectra and are named LHCI-680 and LHCI-730 (2,4,17). Photosystem II (PSII)…”