SMALL CAB-LIKE PROTEINS RETARD CHLOROPHYLL DEGRADATION AND STIMULATE CHLOROPHYLL SYNTHESIS IN SYNECHOCYSTIS SP. PCC 6803: KINETIC ANALYSIS OF PIGMENT LABELING WITH 13C

摘要

Five open reading frames (scpA-scpE) that code for single-helix proteins resembling helices I and III of chlorophyll a/b-binding antenna proteins of higher plants have been identified in Synechocystis sp. PCC 6803 (Funk & Vermaas 1999). Multiple genesencoding SCP (or Hli) proteins have been found in other cyanobac-terial species as well (Bhaya et al 2002). Several cellular functions have been proposed for SCPs, including regulation of pigment synthesis (Xu et al 2002), protection of the photosynthetic apparatus from photooxidative damage (Havaux et al 2003), and involvement in transient chlorophyll binding during assembly or reassembly of pigment-protein complexes in photosystems (PS) (Xu et al 2004). The deletion of the genes for four or five SCPs in PS I-less Synechocystis strains causes a large decrease in the chlorophyll content of the cells (Xu et al 2004).