Continuous Assembly of β-Roll Structures Is Implicated in the Type I-Dependent Secretion of Large Repeat-in-Toxins (RTX) Proteins
Language English Country Netherlands Media print-electronic
Document type Journal Article, Research Support, Non-U.S. Gov't
PubMed
32860773
DOI
10.1016/j.jmb.2020.08.020
PII: S0022-2836(20)30514-3
Knihovny.cz E-resources
- Keywords
- Bordetella pertussis, RTX proteins, adenylate cyclase toxins, type I secretion system,
- MeSH
- Adenylate Cyclase Toxin chemistry genetics metabolism MeSH
- Bacterial Proteins chemistry metabolism MeSH
- Bacterial Toxins chemistry genetics metabolism MeSH
- Bordetella pertussis metabolism MeSH
- Cytosol metabolism MeSH
- Gram-Negative Bacteria metabolism MeSH
- Protein Conformation MeSH
- Protein Folding MeSH
- Type I Secretion Systems MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Names of Substances
- Adenylate Cyclase Toxin MeSH
- Bacterial Proteins MeSH
- Bacterial Toxins MeSH
- Type I Secretion Systems MeSH
Repeats-in-Toxin (RTX) proteins of Gram-negative bacteria are excreted through the type I secretion system (T1SS) that recognizes non-cleavable C-terminal secretion signals. These are preceded by arrays of glycine and aspartate-rich nonapeptide repeats grouped by four to eight β strands into blocks that fold into calcium-binding parallel β-roll structures. The β-rolls are interspersed by linkers of variable length and sequence and the organization of multiple RTX repeat blocks within large RTX domains remains unknown. Here we examined the structure and function of the RTX domain of Bordetella pertussis adenylate cyclase toxin (CyaA) that is composed of five β-roll RTX blocks. We show that the non-folded RTX repeats maintain the stability of the CyaA polypeptide in the Ca2+-depleted bacterial cytosol and thereby enable its efficient translocation through the T1SS apparatus. The efficacy of secretion of truncated CyaA constructs was dictated by the number of retained RTX repeat blocks and depended on the presence of extracellular Ca2+ ions. We further describe the crystal structure of the RTX blocks IV-V of CyaA (CyaA1372-1681) that consists of a contiguous assembly of two β-rolls that differs substantially from the arrangement of the RTX blocks observed in RTX lipases or other RTX proteins. These results provide a novel structural insight into the architecture of the RTX domains of large RTX proteins and support the "push-ratchet" mechanism of the T1SS-mediated secretion of very large RTX proteins.
References provided by Crossref.org
Kingella kingae RtxA Cytotoxin in the Context of Other RTX Toxins
