Mark van Raaij introduces the two new Section Editors who have been appointed to Structural Biology Communications – Acta Cryst. F.

The determination of the first crystal structure of adenylosuccinate lyase (PurB) from Thermus thermophilus HB8 (TtPurB) is described. The structure was compared with other PurB proteins based on r.m.s.d., and molecular dynamics simulations were performed using the full-length model of TtPurB with and without substrate/product.

The bacterial two-component system consisting of the histidine kinase QseE and the response regulator QseF regulates the virulence of Enterobacteriaceae. Its operon also encodes the outer membrane protein QseG. QseG interacts with QseE in the periplasm to constitute a unique three-component system. Crystal structures of the periplasmic regions show that QseE has a helix-bundle structure, while QseG is composed of an N-terminal globular domain and a C-terminal homodimeric coiled-coil. Polymorphism at the end of the coiled-coil indicate flexibility, while its electrostatic surface suggests interaction with QseE.