Chloroplast heat shock protein Cpn60 from Chlamydomonas reinhardtii exhibits a novel function as a group II intron-specific RNA-binding protein.
Intron-binding proteins in eukaryotic organelles are mainly encoded by the nuclear genome and are thought to promote the maturation of precursor RNAs. Here, we present a biochemical approach that enable the isolation of a novel nuclear-encoded protein from Chlamydomonas reinhardtii showing specific binding properties to organelle group II intron RNA. Using FPLC chromatography of chloroplast protein extracts, a 61-kDa RNA-binding protein was isolated and then tentatively identified by mass spectrometry as the chloroplast heat shock protein Cpn60. Heterologous Cpn60 protein was used in RNA protein gel mobility shift assays and revealed that the ATPase domains of Cpn60 mediates the specific binding of two group II intron RNAs, derived from the homologous chloroplast psaA gene and the heterologous mitochondrial LSU rRNA gene. The function of Cpn60 as a general organelle splicing factor is discussed.
Balczun
Carsten
C
Lehrstuhl für Allgemeine und Molekulare Botanik, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
Bunse
Astrid
A
Schwarz
Christian
C
Piotrowski
Markus
M
Kück
Ulrich
U
D000818:Animals; D018834:Chaperonin 60 / Q000302:isolation & purification / Q000502:physiology*; D016825:Chlamydomonas reinhardtii / Q000737:chemistry / Q000235:genetics*; D002736:Chloroplasts / Q000737:chemistry / Q000235:genetics*; D007438:Introns; D013058:Mass Spectrometry; D010940:Plant Proteins / Q000032:analysis / Q000302:isolation & purification / Q000502:physiology*; D012326:RNA Splicing; D016601:RNA-Binding Proteins / Q000032:analysis / Q000302:isolation & purification / Q000378:metabolism*
D018834:Chaperonin 60; D010940:Plant Proteins; D016601:RNA-Binding Proteins