PARENT SESSION
Posters P1A Proton coupled electron transport and ATPase. Abstracts (172-180)

Effect of deletions from the N-terminus on the functions of the subunit of the chloroplast ATP synthase. Zhang-Lin Ni^*,1, Jia-Mian Wei¹, ¹ Shanghai Institute of Plant Physiology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China

ABSTRACT- Five truncation mutants of chloroplast ATP synthase subunit from spinach (Spinacia oleracea) lacking 8, 12, 16, 20 or 60 amino acid residues from the N-terminus, were generated by PCR by a mutagenesis method. The recombinant genes were overexpressed in E. coli and assembled with a native complex. The WT assembly exhibited high Mg²⁺- or Ca²⁺- ATPase activities. Deletions of 8 residues of the subunit N-terminus caused decrease in rates of ATP hydrolysis to 30% of that of WT assembly. Furthermore, only about 6% of rates of ATP hydrolysis was retained with the sequential deletions of subunit up to 20 residues compared with the activities of WT assembly. The inhibitory effect of the subunit on ATP hydrolysis of those assemblies varied to a large extent. These observations indicate that the subunit N-terminal end is very important, together with other regions of the subunit, in stabilization of the enzyme complex or during cooperative catalysis. In addition, the in vitro binding assay showed that the subunit N-terminus is not a crucial region contributing to the binding of the subunit.

KEY WORDS: assembly, the subunit, GST pull-down assay