title: Tetratricopeptide-like repeats in type-III-secretion chaperones and regulators.
abstract: Efficient type-III secretion depends on cytosolic molecular chaperones, which bind specifically to the translocators and effectors. In the past there has been a tendency to shoe-horn all type-III-secretion chaperones into a single structural and functional class. However, we have shown that the LcrH/SycD-like chaperones consist of three central tetratricopeptide-like repeats that are predicted to fold into an all-alpha-helical array that is quite distinct from the known structure of the SycE class of chaperones. Furthermore, we predict that this array creates a peptide-binding groove that is utterly different from the helix-binding groove in SycE. We present a homology model of LcrH/SycD that is consistent with existing mutagenesis data. We also report the existence of tetratricopeptide-like repeats in regulators of type-III secretion, such as HilA from Salmonella enterica and HrpB from Ralstonia solanacearum. The discovery of tetratricopeptide-like repeats in type-III-secretion regulators and chaperones provides a new conceptual framework for structural and mutagenesis studies and signals a potential unification of prokaryotic and eukaryotic chaperone biology.
authors.affiliation: Division of Immunity and Infection, Medical School, University of Birmingham, Birmingham, B15 2TT, UK. mpallen@bham.ac.uk
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Pallen
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Francis
authors.forename: Klaus
authors.initials: K
authors.lastname: Fütterer
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics; D018832:Molecular Chaperones / Q000737:chemistry* / Q000235:genetics*; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012091:Repetitive Sequences, Nucleic Acid; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D018832:Molecular Chaperones; C118339:SycD protein, bacteria