TABLE 3.

Glycosylation turnover rates and dissociation constants for sequon and PglB variants affecting interactions at −2 position

Turnover rates and dissociation constants were derived from curves shown in supplemental Figs. S2 and S4. The errors represent the S.E. of the fit for each turnover rate and dissociation constant. Values for relative turnover and relative binding refer to the ratio of an individual mutant/sequon and WT PglB/DQNAT sequon.

Mutant	Sequon	Turnover rate	Relative turnover/fold reduction	Dissociation constant (Kd)
		peptide/s		μm
WT	DQNAT	1.50 ± 0.04	1	1.02 ± 0.06
WT	AQNAT	(3.08 ± 0.13) × 10−5	2.05 × 10−5/50,000-fold	–a
R331A	DQNAT	(3.71 ± 0.08) × 10−3	2.47 × 10−3/400-fold	–a
R331A	AQNAT	(1.03 ± 0.02) × 10−4	6.87 × 10−5/15,000-fold	NDb

^a Peptide binding was observed, but no K_d could be determined because the fluorescence anisotropy signal reached only 30–50% saturation at the limiting PglB concentration of 100–150 μm.

^b ND, data not determined.