Light-dependent assembly of ribulose-1,5-bisphosphate carboxylase
AUTOR(ES)
Bloom, Mark V.
RESUMO
Ribulose-1,5-bisphosphate carboxylase [RuP2Case; 3-phospho-D-glycerate carboxy-lyase (dimerizing), EC 4.1.1.39] is composed of eight small subunits (Mr, 14,000) and eight large subunits (Mr, 55,000). Newly synthesized large subunits are associated with two complexes having sedimentation coefficients of 7 and 29 S. Assembly of RuP2Case occurs in isolated intact chloroplasts in the light but not in the dark. When extracts of chloroplasts are treated with ATP or GTP, RuP2Case assembly is accelerated while the 29S large subunit complex is maintained. In the presence of Mg2+, ATP brings about almost complete dissociation of the 29S complex, whereas GTP and a nonhydrolyzable analog of ATP are without effect. These results indicate the existence of a complex set of reactions involving nucleotides, Mg2+, and several putative intermediates in RuP2Case assembly. It is postulated that these reactions at least partly account for the light dependence of RuP2Case assembly. In particular, ATP and GTP promote the assembly of large subunits into RuP2Case.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=393518Documentos Relacionados
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