Non-Repeat Segment 1 in Vibrio vulnificus MARTX toxin, which binds to biantennary N-glycans, is essential for host cell blebbing but dispensable for effector translocation

We read with interest the article by Dr. Satchell and her colleagues, published on bioRxiv, titled “Biantennary N-glycans as Receptors for MARTX Toxins in Vibrio Pathogenesis” (Chen et al., 2024). In that article, the authors utilize AlphFold2 to predict the structure of the repeat-containing regions of the pore-forming multifunctional autoprocessing repeats–in–toxin (MARTX_Vv) toxin from Vibrio vulnificus and identify tandem immunoglobulin-like folds, which they refer to as Aknot. Through a series of compelling biochemical and cell–biological analyses, they demonstrate that Aknot interacts with biantennary N-glycans on host cell surface glycoproteins. Furthermore, by showing reduced cytotoxicity and virulence in V. vulnificus variants secreting an Aknot–deleted MARTX toxin, they argue that the absence of Aknot renders the MARTX_Vv toxin incapable of forming pores in host cell membranes. While these findings provide important insights into the host receptors involved in MARTX toxin binding, our independent study—employing systematic deletions in the repeat-containing regions of MARTX_Vv and examining their effects on MARTX intoxication processes—reveals that the Aknot region (termed ‘NRS1’ in our study) is dispensable for effector translocation, despite being essential for host cell blebbing and lysis. To both support the Satchell group's findings and clarify potential misconceptions regarding the role of Aknot/NRS1, we summarize our results here.