Subategory:

Mutants

Description:

The 45-3B chloroplast mutant was recovered by screening a collection of acetate-requiring mutants for lack of complementation with a known Rubisco rbcL mutant. The mutant was crossed with pf2 mt- to confirm uniparental inheritance, and this mt+ progeny clone was analyzed. Mutant 45-3B results from a V331A substitution (GTT-GCT) in the chloroplast-encoded large subunit of Rubisco, which causes decreases in Rubisco CO₂/O₂ specificity and carboxylation catalytic efficiency. The V331A mutant-enzyme x-ray crystal structure has been solved. Selection for photosynthesis-competent revertants yielded true revertants and intragenic suppressors. Other types of revertants have been recovered. This strain has been maintained with acetate medium in darkness since its isolation.

Species:

Chlamydomonas

Locus:

rbcL

Chromosome:

Chloroplast

Phenotype:

Requires acetate; sensitive to light