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. 1988 Oct;85(19):7109–7113. doi: 10.1073/pnas.85.19.7109

Coordinated assembly of multisubunit proteins: oligomerization of bacterial enterotoxins in vivo and in vitro.

S J Hardy 1, J Holmgren 1, S Johansson 1, J Sanchez 1, T R Hirst 1
PMCID: PMC282133  PMID: 3050987

Abstract

In this paper we study the assembly, in vivo and in vitro, of a family of hexameric, heat-labile enterotoxins produced by diarrheagenic bacteria. The toxins, which consist of an A subunit and five B subunits, are assembled by a highly coordinated process that ensures secretion of the holotoxin complex. We show that (i) oxidation of cysteine residues in the B subunits is a prerequisite step for in vivo formation of B-subunit pentamers, (ii) reduction of dissociated B subunits in vitro abolishes their ability to reassemble, (iii) the kinetics of B-pentamer assembly in vivo can be mimicked under defined conditions in vitro, (iv) A subunits cannot associate with fully assembled B pentamers in vitro, and (v) A subunits cause an approximately 3-fold acceleration in the rate of B-subunit pentamerization in vivo, implying that A subunits play a coordinating role in the pathway of holotoxin assembly. The last finding is likely to be of general significance, since it provides a mechanism for preferentially excluding or favoring certain intermediates in the assembly of multisubunit proteins.

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Selected References

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