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. Author manuscript; available in PMC: 2009 Mar 14.
Published in final edited form as: J Mol Biol. 2007 Dec 15;377(1):148–161. doi: 10.1016/j.jmb.2007.12.025

Figure 5.

Figure 5

Slow formation of LexA heterodimers. (a) LexA and the cleavage fragment (X) from WT/ΔN; (b) WT/ΔN and the cleavage fragment (X) from WT/ΔN; (c) LexA and WT/ΔN. In each case, proteins were mixed together (at final concentrations 5 μM each) and incubated at 30°C. At the indicated times (in min) aliquots were mixed with glutaraldehyde to 16 mM. After 30 s, reactions were stopped with glycine to 160 mM. Samples were run on 15% Laemmli gels and stained with Coomassie blue. Bands are labeled: L, full-length LexA monomer; X, cleaved WT/ΔN monomer; and Δ, WT/ΔN monomer. Dimers are labeled by combinations of these labels; e.g., L-Δ, LexA-WT/ΔN heterodimer. In (d), a representative experiment is shown when 0.5 μM LexA and 0.5 μM labeled WT/PKA were cross-linked as above. The counts in the heterodimer band were compared to the sum of the counts in the homodimer and heterodimer bands. Data varied by 10-20% between experiments. Within 2 h, 50 ± 8% of the labeled protein was in the heterodimer.