Evidence of monomeric photosystem I complexes and phosphorylation of chlorophyll a/c-binding polypeptides in Chroomonas sp. strain LT (Cryptophyceae).
Thylakoid membranes of the cryptophyte Chroomonas sp. strain LT were solubilized with dodecyl-beta-maltoside and subjected to sucrose density gradient centrifugation. The four pigment protein complexes obtained were subsequently characterized by absorption and fluorescence spectroscopy, SDS-PAGE, and Western immunoblotting using antisera against the chlorophyll a/c-binding proteins of the marine cryptophyte Cryptomonas maculata and the reaction-center protein D2 of photosystem II of maize. Band 1 consisted mainly of free pigments, phycobiliproteins, and chlorophyll-a/c-binding proteins. Band 2 represented a major chlorophyll a/c-binding protein fraction. A mixture of photosystem II and photosystem I proteins comprised band 3, whereas band 4 was enriched in proteins of photosystem I. Western immunoblotting demonstrated the presence of chlorophyll a/c-binding proteins and their association with photosystem I in band 4. Phosphorylation experiments showed that chlorophyll a/c-binding proteins became phosphorylated. Negative staining electron microscopy of band B4 revealed photosystem I particles with dimensions of 22 nm. Our work showed that PSI-LHCI complexes of cryptophytes are similar to those of Chlamydomonas rheinhardtii, the diatom Phaeodactylum tricornutum, and higher plants.
Geomicrobiology, ICBM, Carl-von-Ossietzky-University of Oldenburg, Oldenburg, Germany.
Julia
J
Janssen
Erhard
E
Rhiel
D002499:Centrifugation, Density Gradient; D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D044785:Cryptophyta / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D019281:Dimerization; D045342:Light-Harvesting Protein Complexes / Q000378:metabolism; D008320:Maltose / Q000031:analogs & derivatives / Q000378:metabolism; D008854:Microscopy, Electron; D010455:Peptides / Q000378:metabolism*; D010766:Phosphorylation; D045331:Photosystem I Protein Complex / Q000737:chemistry / Q000378:metabolism*
D045342:Light-Harvesting Protein Complexes; D010455:Peptides; D045331:Photosystem I Protein Complex; D002734:Chlorophyll; C064041:chlorophyll c; D008320:Maltose; D000077194:Chlorophyll A