Subategory:

Mutants

Description:

The 69-12Q chloroplast mutant was recovered by screening a collection of acetate-requiring mutants for lack of complementation with a known Rubisco rbcL mutant. It results from a T173I substitution (ACA-ATA) in the chloroplast-encoded large subunit of Rubisco, which eliminates carboxylase activity but not Rubisco holoenzyme assembly. This active-site residue is normally Ile in Rhodospirillum rubrum Rubisco, and replacing that residue with Thr also causes a decrease in carboxylase activity. Selection for photosynthesis-competent revertants of rbcL-T173I yielded only true revertants. This strain was recovered from a cross between the original 69-12Q mt+ and pf2 mt-, and has been maintained with acetate medium in darkness since its isolation.

Species:

Chlamydomonas

Locus:

rbcL

Chromosome:

Chloroplast

Phenotype:

Requires acetate; sensitive to light