The 70-kDa heat shock protein/DnaK chaperone system is required for the productive folding of ribulose-bisphosphate carboxylase subunits in Escherichia coli

SUSANA KARINA CHECA; VIALE, A. M.

EUROPEAN JOURNAL OF BIOCHEMISTRY

Blackwell Publishing Ltd

Lugar: England; Año: 1997 vol. 248 p. 848 - 855

0014-2956

We have studied the in vivo requirements of the DnaK chaperone system for the folding of recombinantribulose-bisphosphate carboxylase/oxygenase in Esc-hrrichia coli. Expression of functional dimericor hcxadecaineric ribulose-bisphosphate carboxylase from different bacterial sources (including purplebacteria and cyanobacteria) was severely impaired in E. coli dnaK, tltztrJ, or grpE mutants. These enzymeswere synthesized mostly in soluble, fully enzymatically active forms in wild-type E. t.o/i cells culturedin the temperature range 20-42"C, but aggregated extensively in rlnaK null mutants. Co-expression ofdtuK, but not groESL, markedly reduced the aggregation of ribulose-bisphosphate carboxylase subunitsin dnnK null mutants and restored the enzyme activity to levels found in isogenic wild-type strains.Ribulose-bisphosphate carboxylase expression in wild-type E. coli cells growing at 30°C promoted anenhanced synthesis of stress proteins, apparently by sequestering DnaK from its negative regulatory rolein this responsc. The overall results indicate that the DnaK chaperone system assists in vivo the foldingpathway of ribulose-bisphosphate carboxylase large subunits, most probably at its very early stages.