IbpA the small heat shock protein from Escherichia coli forms fibrils in the absence of its cochaperone IbpB

Small heat shock proteins (sHsps) associate with aggregated proteins, changing their physical properties in such a way that chaperone mediated disaggregation becomes much more efficient. In Escherichia coli two small Hsps, IbpA and IbpB, exist. They are 48% identical at the amino acid level, yet their roles in stabilisation of protein aggregates are quite distinct. Here we analysed the biochemical properties of IbpA. We found that IbpA assembles into protofilaments which in turn form mature fibrils. Such fibrils are atypical for sHsps. Interaction of IbpA with either its cochaperone IbpB or an aggregated substrate blocks IbpA fibril formation. Structured summary: MINT-7876715: ibpA (uniprotkb:P0C054) and ibpA (uniprotkb: P0C054) bind (MI:0407) by molecular sieving (MI: 0071) MINT-7888427: ibpB (uniprotkb:P0C058) and ibpB (uniprotkb: P0C058) bind (MI: 0407) by molecular sieving (MI: 0071) MINT-7888448: ibpA (uniprotkb: P0C054) and ibpA (uniprotkb: P0C054) bind (MI: 0407) by electron microscopy (MI: 0040) MINT-7888434: ibpB (uniprotkb: P0C058) and ibpB (uniprotkb: P0C058) bind (MI: 0407) by electron microscopy (MI: 0040) MINT-7888459: ibpA (uniprotkb: P0C054) and ibpA (uniprotkb: P0C054) bind (MI: 0407) by fluorescence microscopy (MI: 0416) (C) 2010 Federation of European Biochemical Societies. Published by Elsevier B.V. All rights reserved.