TABLE 5.

Purine phosphoribosyltransferase activity and purine uptake in mutants of H. halobium and H. volcanii resistant to purine analogs^a

Organism	Phenotype of mutant	Strain	Phosphoribosyltransferase activity (nmol/min/mg of protein)			Uptake (nmol/min/mg of protein)
			Ade	Hyp	Gua	Ade	Hyp	Gua
H. halobium	Wild type	Hh1	2.05	2.34	0.87	0.65	0.40	0.19
	8-Azaadenine resistant	Hh11	<0.01	4.57	—	0.02	0.59	0.30
		Hh12	<0.01	4.14	—	0.04	0.52	0.26
	8-Azaguanine resistant	Hh15	—	3.30	0.78	0.81	0.31	0.25
		Hh16	—	0.05	<0.01	0.81	0.09	0.10
		Hh18	—	2.10	0.37	0.96	0.12	0.07
H. volcanii	Wild type	WFD11	1.43	2.13	2.45	0.31	0.25	0.23
	2-Fluoroadenine resistant	Hv166	<0.01	4.30	—	0.13	0.38	0.34
		Hv174	<0.01	5.70	—	0.01	0.13	0.21
	8-Azaguanine resistant	Hv105	—	<0.01	0.07	—	0.01	0.01
		Hv118	—	2.32	2.48	—	0.03	0.02

^aAde, adenine; Hyp, hypoxanthine; Gua, guanine; —, not determined. Values are averages of two independent experiments.