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Mutations in loop six of the large subunit of ribulose-1,5-bisphosphate carboxylase affect substrate specificity

M.A.J. Parry, P. Madgwick, S. Parmar, M.J. Cornelius and A.J. Keys
Planta
Vol. 187, No. 1 (1992), pp. 109-112
Published by: Springer
Stable URL: http://www.jstor.org/stable/23381498
Page Count: 4
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Mutations in loop six of the large subunit of ribulose-1,5-bisphosphate carboxylase affect substrate specificity
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Abstract

Mutagenesis in vitro of the gene encoding the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) from Anacystis nidulans (Synechococcus PCC 6301) was used to generate novel enzymes in Escherichia coli. Residues in C-terminal loop 6 of the β/α barrel structure of the large subunit were changed. Replacement of valine 331 with alanine caused a 90% reduction in Vmax but did not alter the enzyme's relative specificity towards either of its gaseous substrates, CO2 and O2. However replacement of alanine 340 with glutamate decreased the enzyme's specificity for CO2 but had no significant effect on either the Km for ribulose-1,5-bisphosphate or CO2 or on Vmax. In contrast replacing a small cassette of residues 338—341 produced a small increase in the specificity factor.

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