Abstract
Helicobacter pylori is a Gram-negative bacterium that causes chronic inflammations in the stomach area and is involved in ulcers, which can develop into gastric malignancies. H. pylori attaches and colonizes to the human epithelium using some of their outer membrane proteins (OMPs). HomB and HomA are the most studied OMPs from H. pylori as they play a crucial role in adherence, hyper biofilm formation, antibiotic resistance and are also associated with severe gastric malignancies. The role of HomA and HomB in pathogenesis concerning their structure and function has not been evaluated yet. In the present study, we explored the structural aspect of HomA and HomB proteins using various computational, biophysical and small-angle X-ray scattering (SAXS) techniques. Interestingly, the in-silico analysis revealed that HomA/B consists of 8 discontinuous N and C terminal β-strands forming a small β-barrel, along with a large surface-exposed globular domain. Further, biophysical experiments suggested that HomA and HomB are dimeric and most likely the cysteine residues present on surface-exposed loops participate in protein–protein interactions. Our study provides essential structural information of unexplored proteins of the Hom family that can help in a better understanding of H. pylori pathogenesis.
Highlights
Gastric cancer is the second most common cause of cancer-associated deaths[1]
Oleastro et al investigated pathogenesis and immunological response caused by HomB protein in clinical patients and 190 H. pylori strain isolated from patients with peptic ulcer disease (PUD) or gastritis were evaluated for the clinical importance of homB
Helicobacter pylori is the major cause of several stomach diseases
Summary
Gastric cancer is the second most common cause of cancer-associated deaths[1]. Chronic gastritis is the major cause of human gastric cancer caused by the Gram-negative bacterium Helicobacter pylori. Large β-barrel proteins have been characterized, such as 26 β-strands LptD from Shigella flexneri15, 24-stranded β-barrel PapC from E. coli[16] These β-barrel proteins contain the transmembrane domains which interact with the host cell receptors. These proteins form a porin-like structure and act as efflux pumps, and are involved in the transport of metabolites, such as BtuB, O prM17,18. These transmembrane β-barrels can exist as monomers or oligomers, for example, OmpF from Salmonella typhimurium forms a trimer of β-barrel[19]. Extensive inter-strand hydrogen bonding with the non-polar lipid bilayer and the existence of aromatic residues at the water-bilayer interface anchor them in the lipid bilayer and result in highly stable transmembrane β-barrels, which do not unfold e asily[21,22,23]
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