Fig. 10: Schematic for an updated cap model for sheath polymerisation. | Nature Communications

Fig. 10: Schematic for an updated cap model for sheath polymerisation.

From: Functionality of chimeric TssA proteins in the type VI secretion system reveals sheath docking specificity within their N-terminal domains

Fig. 10

A TssA complex (light blue), formed of a ring structure with flexibly associated Nt1 domains, is bound at the distal end of the sheath (grey). For simplicity, a subset of Nt1 domains is represented, but in reality, many more would be flexibly associated with the ring. Interaction between TssA and the sheath is mediated by Nt1 domains which insert in binding grooves at the tip of the sheath. In this model, an unbound Nt1 domain can recruit a free sheath subunit, whose incorporation into the distal end of the sheath generates a conformational change that displaces a neighbouring TssA Nt1 domain subunit from its binding groove. Through this process, new sheath subunits are incorporated while TssA remains bound.

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