Table 2.

Enzymatic activity of WT and mutants bc₁

bc1 mutants	Bovine equivalent	Photosynthetic growth	Specific activity*		Km	Note	Source
			Purified Rsbc1	Chromatophore
Bovine bc1		—	20.0	—	N/A	Having a KS dyad in cyt b with two H-bonds to ISP	This work
Wt Rsbc1		+++++	2.5	2.2	1.56	Having no KS dyad still with two H-bonds to ISP	This work
KS dyad mutants
G167S	S151	+++++	2.4	1.9	1.50	Forming a KS dyad, presumably leading to two H-bonds	This work
S322A		++++†	0.76	0.67	2.00	Single mutation in the ef1 insertion in rsbc1	This work
Δ(309–326)		++++†	0.48	0.46	1.45	Deletion mutant of the ef1 insertion in rsbc1	This work
Δ(309–326)/    G167S		++++†	0.46	0.34	1.39	Double mutations mimicking bovine bc1 with the KS dyad	This work
SC mutant
W142R,K,T,S	W141	—	—	—	—	Respiration incapable in yeast, c+c1 reduction kinetics severely affected	Ref. 25
T160S,Y	T144	—	—	—	—	70–80% lower activity in rsbc1	Ref. 26
292F	I268	—	—	—	—	Incapable of photosynthetic growth in R.s., affecting QH2 oxidation	Ref. 27
L282F	L281	—	—	—	—	Respiration incapable in yeast	Ref. 28
L305A,D	L281	—	—	—	—	Slow QH2 oxidation in rsbc1	Ref. 27
K329A	K287	++++†	0.9	0.8	1.40	Mutant that has lowered QH2 oxidation activity in rsbc1 and changes the shape complementarity	This work and ref. 27

*Enzymatic activity is expressed as μmol of cyt c reduced per min/nmol cyt b at room temperature. The concentration of cyt c in assay mixture is 50 μM.

^†Delayed by >12 h.