Immunoelectron microscopic analysis of the A, B, and HU protein content of bacteriophage Mu transpososomes - PubMed (original) (raw)

. 1990 Jan 25;265(3):1623-7.

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Immunoelectron microscopic analysis of the A, B, and HU protein content of bacteriophage Mu transpososomes

B D Lavoie et al. J Biol Chem. 1990.

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Abstract

Stable protein-DNA complexes or transpososomes mediate the Mu DNA strand transfer reaction in vitro (Surette, M. G., Buch, S. J., and Chaconas, G. (1987) Cell 49, 253-262; Craigie, R., and Mizuuchi, K. (1987) Cell 51, 493-501). Formation of the Type 1 complex, an intermediate in the strand transfer reaction, requires the Mu A and Escherichia coli HU proteins. Generation of the Type 2 complex, in which the Mu ends have been covalently linked to the target DNA, requires the Mu B protein, ATP, and target DNA in addition to A and HU. The protein content of these higher order synaptic complexes has been studied by immunoelectron microscopy using protein A-colloidal gold conjugates to visualize antibody-bound complexes. Under our in vitro transposition conditions, Type 1 complexes were found to contain A and HU; in addition, Type 2 complexes contained Mu B. However, both the HU and the Mu B protein were found to be loosely associated and could be quantitatively removed from the nucleoprotein core of both complexes by incubation in 0.5 M NaCl. Depletion of HU from the Type 1 complex did not affect the ability of this complex to be converted into the strand-transferred product. Hence, the indispensable role of the HU protein in the Mu DNA strand transfer reaction is limited to the formation of the Type 1 transpososome.

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