Subategory:

Mutants

Description:

Using standard methods of directed mutagenesis and chloroplast transformation of rbcLΔ-MX3312 mt+ (MUT-4696), a C256A substitution (TGT-GCT) was created in the Rubisco large subunit. Because Cys-256 is methylated, this mutant was created to investigate the role of the modified residue in Rubisco structure or function. Large-subunit Cys-256 has significant interactions with the Rubisco small subunit. The C256A substitution causes decreases in Rubisco CO₂/O₂ specificity and carboxylation catalytic efficiency. The mutant strain grows slowly on minimal medium at 25 °C, but dies on minimal medium at 35 °C. This strain has been maintained with acetate medium in darkness to prevent selection for secondary mutations that may improve Rubisco function.

Species:

Chlamydomonas

Locus:

rbcL

Chromosome:

Chloroplast

Phenotype:

Requires acetate at 35 °C; temperature-conditional