Table I.

Summary of SMR Data of HIV-2 Proteases

		Molecular masses estimated by SMRa (g/mol)
Construct	Inhibitor DRVb	Mexperimental	Mcalcc(monomer)	Mexperimental/Mcalc(monomer)	Major species
PR2	−	22,400 ± 336	10,719	2.09 ± 0.03	Dimer
	+	19,555 ± 156		1.82 ± 0.02	Ternary complex
PR2-2M	−	21,790 ± 501		2.03 ± 0.05	Dimer
	+	20,590 ± 165		1.92 ± 0.02	Ternary complex
PR2-4M	−	14,670 ± 205		1.37 ± 0.02	Dimer + monomer
	+	19,170 ± 326		1.79 ± 0.03	Ternary complex
PR2D25N	−	21,900 ± 635	10844	2.02 ± 0.06	Dimer
	+	24,620 ± 591		2.27 ± 0.06	Ternary complex
PR2T26A	−	11,170 ± 179	11293	0.99 ± 0.02	Monomer
	+	11,150 ± 133		0.99 ± 0.01	Monomer
PR21–95	−	10,570 ± 180	10292	1.03 ± 0.02	Monomer
	+	10,510 ± 315		1.02 ± 0.03	Monomer

^aProteins were fractionated on a Superdex-75 column at room temperature equilibrated in 50 mM sodium acetate, pH 5, 50 mM NaCl. The notations 2M and 4M indicate the presence of 2 and 4M urea, respectively, in the sample and column eluant.

^bProteins either in the absence or added to 1.1-fold excess of inhibitor darunavir (DRV).

^cM_calc indicates the monomer mass of unlabeled PR2, ¹³C ¹⁵N-labeled PR2_T26A, and ¹⁵N-labeled PR2_D25N and PR2_1–95 proteins.