Premium
Comparative analysis of the secretion capability of early and late flagellar type III secretion substrates
Author(s) -
Singer Hanna M.,
Erhardt Marc,
Hughes Kelly T.
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12675
Subject(s) - secretion , signal peptide , biology , secretory protein , secretory pathway , microbiology and biotechnology , cytoplasm , translation (biology) , messenger rna , biochemistry , peptide sequence , gene , golgi apparatus , endoplasmic reticulum
Summary A remarkable feature of the flagellar‐specific type III secretion system ( T3SS ) is the selective recognition of a few substrate proteins among the many thousand cytoplasmic proteins. Secretion substrates are divided into two specificity classes: early substrates secreted for hook‐basal body ( HBB ) construction and late substrates secreted after HBB completion. Secretion was reported to require a disordered N‐terminal secretion signal, mRNA secretion signals within the 5′‐untranslated region (5′‐ UTR ) and for late substrates, piloting proteins known as the T3S chaperones. Here, we utilized translational β‐lactamase fusions to probe the secretion efficacy of the N ‐terminal secretion signal of fourteen secreted flagellar substrates in S almonella enterica . We observed a surprising variety in secretion capability between flagellar proteins of the same secretory class. The peptide secretion signals of the early‐type substrates FlgD , FlgF , FlgE and the late‐type substrate FlgL were analysed in detail. Analysing the role of the 5′‐ UTR in secretion of flgB and flgE revealed that the native 5′‐ UTR substantially enhanced protein translation and secretion. Based on our data, we propose a multicomponent signal that drives secretion via the flagellar T3SS . Both mRNA and peptide signals are recognized by the export apparatus and together with substrate‐specific chaperones allowing for targeted secretion of flagellar substrates.