PARENT SESSION
Posters P6B Photosynthetic acclimation: Mechanisms and gene expression. Abstracts (531-578)

TCP34, an unique response regulator-like TPR protein of higher plant chloroplasts. Anna Sokolenko^*,1, Petra Weber², Hrvoje Fulgosi³, Irina Piven¹, Lenard Müller⁴, Karin Krupinska⁴, Reinhold G. Herrmann¹, ¹ Department Biologie I, Botanik, 80638 Munich, Germany² Institut für Neuropathologie, 81377 Munich, Germany³ Department of Molecular Genetics, Zagreb, Croatia⁴ Institut für Botanik, 24098 Kiel, Germany

ABSTRACT- We identified a nucleus-encoded 37.2 kDa precursor protein representing a novel molecular component in chloroplasts. Due to the presence of three tandemly arranged TPR arrays the novel chloroplast protein was designated TCP34 (tetratricopeptide-containing chloroplast protein of 34 kDa). The in vitro translated precursor could be imported into intact spinach chloroplasts and showed stable association with thylakoid membranes. Using a specific polyclonal antiserum raised against TCP34 three protein variants were detected, two forms associated with the thylakoid membranes and a processed stroma form lacking the C-terminal transmembrane domain. The higher molecular weight thylakoid membrane and stromal TCP34 forms were found to be phosphorylated. The combination of a centrally positioned tetratricopeptide repeat (TPR) array with a N-terminal response regulator-like domain, integrating a putative helix-loop-helix motif, suggests an intriguing regulatory molecule. TCP34 was found in association with a transcriptionally active protein/DNA complex (TAC, transcriptionally active chromosomes)and recombinant TCP34 showed specific binding to Spinacia oleracea chloroplast DNA (ptDNA). An as yet unidentified phosphorelay signal may modulate its capability for ptDNA binding through the phosphorylation state of the putative response regulator-like domain. Based on the structural properties and biochemical analyses we propose a possible regulatory role for TCP34 in a plastid gene expression.

KEY WORDS: gene expression, signal transduction, TPR array, DNA-binding