Table 1. Cyclase activity upon reconstitution of plastid P and S fractions from xantha-l³⁵, xantha-l⁸¹, and viridis-k²³ mutants with wild-type fractions.

	Fractions in incubation
Exp. no.	P fraction		S fraction	Cyclase activity
1	xan-l35	+	xan-l35	0
	WT	+	xan-l35	99 ± 0
	xan-l35	+	WT	0
	WT	+	WT	76 ± 3
2	xan-l81	+	xan-l81	0
	WT	+	xan-l81	284 ± 8
	xan-l81	+	WT	0
	WT	+	WT	309 ± 3
3	vir-k23	+	vir-k23	0
	WT	+	vir-k23	113 ± 12
	vir-k23	+	WT	0
	WT	+	WT	134 ± 2

Primary leaves from wild-type and homozygous mutant seedlings were harvested simultaneously, and chloroplast fractions were prepared. Cyclase assays were under standard incubation conditions, with the combinations of fractions shown. Protein amounts in the assay for each experiment were as follows. Experiment 1: wild-type P, 70 μg; xantha-l³⁵ P, 90 μg; wild-type S, 300 μg; xantha-l³⁵ S, 400 μg. Experiment 2: wild-type P, 110 μg; xantha-l⁸¹ P, 80 μg; wild-type S, 230 μg; xantha-l⁸¹ S, 240 μg. Experiment 3: wild-type P, 80 μg; viridis-k²³ P, 70 μg; wild-type S, 300 μg; viridis-k²³ S, 400 μg. Cyclase activity is given in pmol of protochlorophyllide formed per mg of protein for every 20-min period.