Salmonella enterica SpvB ADP-Ribosylates Actin at Position Arginine-177Characterization of the Catalytic Domain within the SpvB Protein and a Comparison to Binary Clostridial Actin-ADP-Ribosylating Toxins

Abstract

The SpvB protein from Salmonella enterica was recently discovered as an actin-ADP-ribosylating toxin. SpvB is most likely delivered via a type-III secretion system into eukaryotic cells and does not have a binding/translocation component. This is in contrast to the family of binary actin-ADP-ribosylating toxins from various Bacillus and Clostridium species. However, there are homologies in amino acid sequences between the C-terminal domain of SpvB and the catalytic domains of the actin-ADP-ribosylating toxins such as C2 toxin from Clostridium botulinum and iota toxin from Clostridium perfringens. We compared the biochemical properties of the catalytic C-terminal domain of SpvB (C/SpvB) with the enzyme components of C2 toxin and iota toxin. The specificity of C/SpvB concerning the modification of G- or F-actin was comparable to the C2 and iota toxins, although there were distinct differences regarding the recognition of actin isoforms. C/SpvB and iota toxin modify both muscle alpha-actin and nonmuscle beta/gamma-actin, whereas C2 toxin only modifies beta/gamma-actin. In contrast to the iota and C2 toxins, C/SpvB possessed no detectable glycohydrolase activity in the absence of a protein substrate. The maximal reaction rates were comparable for all toxins, whereas variable K(m) values for NAD were evident. We identified arginine-177 as the modification site for C/SpvB with the actin homologue protein Act88F from Drosophila.

A Salmonella enterica serovar Typhi plasmid induces rapid and massive apoptosis in infected macrophages

“…Intracellular expression of the SpvB protein induces not only disruption of actin filaments, but also apoptotic cell death in eukaryotic cells. 3,24,25 We found a gene sequence that is homologous to spvB on the pR ST98 plasmid. However, pR ST98 is a large chimeric plasmid containing complex sequences of unknown functions.…”

Impact ofSalmonella entericaType III Secretion System Effectors on the Eukaryotic Host Cell

“…The C-terminal domain possesses ADPribosyltransferase activity that covalently modifies G-actin monomers at arginine-177 and prevents their polymerization into F-actin filaments [308][309][310][311]. SpvB inhibits the formation of vacuole-associated actin polymerizations (VAPs) in HeLa cells [312] and negatively regulates the formation of SIFs [313].…”

Association of Three Plasmid-Encoded spv Genes Among Different Salmonella Serotypes Isolated from Different Origins

“…SpvB prevents actin polymerization by ADP-ribosylation of actin monomers. The C-terminal domain of SpvB contains ADPribosyltransferase activity that covalently modifies G-actin monomers and prevents their polymerization into F-actin filaments [12]. Since F-actin is continuously formed and depolymerized in the cell, the activity of SpvB in the host cell cytoplasm leads to loss of the F-actin cytoskeleton [13], furthermore, SpvB is required for Salmonella proliferation in a subset of monocyte derived human macrophages, and is responsible for the late apoptosis seen in host cells during Salmonella infection [14].…”