Crystal structure of a small heat‐shock protein from Xylella fastidiosa reveals a distinct high‐order structure

Citrus variegated chlorosis is a disease that attacks economically important citrus plantations and is caused by the plant‐pathogenic bacterium Xylella fastidiosa. In this work, the structure of a small heat‐shock protein from X. fastidiosa (XfsHSP17.9) is reported. The high‐order structures of small heat‐shock proteins from other organisms are arranged in the forms of double‐disc, hollow‐sphere or spherical assemblies. Unexpectedly, the structure reported here reveals a high‐order architecture forming a nearly square cavity. The structure of XfsHSP17.9, a small heat‐shock protein (sHSP) from X. fastidiosa, is similar to those of other sHSPs, having a conserved structural organization. The secondary structure of XfsHSP17.9 is mostly composed of β‐strands and a few short α‐helices. The XfsHSP17.9 structure reported here reveals a high‐order architecture forming a nearly square cavity.