Table 5.

Aggregation properties of wild-type and mutant β-lactamases

	Wild type	L76N	M182T	L76N:M182T
% inclusion bodies*	21  ± 7	31  ± 2	13  ± 5	19  ± 5
Light scattering at 350 nm†	None	+	None	None
% activity recovered‡	82  ± 11	7  ± 12	65  ± 10	62  ± 4

^*The percentage of β-lactamase protein found in periplasmic inclusion body preparations as a percentage of the β-lactamase in whole-cell extracts. The amount of β-lactamase protein was determined by densitometric quantitation of Western blots from multiple (n = 4–6) independent experiments. 

^† Aggregation was recorded as light scattering at 350 nm after diluting periplasmic extracts from a GdnHCl concentration of 6M into 100 mM sodium phosphate buffer, pH 7.0. The final GdnHCl was 0.88 M. 

^§ Activity recovered after completion of refolding was measured using ampicillin as the substrate. Averages are from multiple, independent experiments (n = 5–7). Per cent recovered activity was based on the activity of non-denatured extracts, which had the same final concentration of GdnHCl.