Structural and functional studies of HomA and HomB, outer membrane proteins of Helicobacter pylori

Abstract

We are surrounded by incredible kinds of living microorganisms that are invisible to our naked eyes and present almost everywhere. Several of these microbes live with us and within us, and are vital for our survival, as they protect the skin from the external parasites, aid in the synthesis of vitamins, digestion of food and nutrient absorption, as well as train the immune system to fight against infectious agents. Nevertheless, some of these microbes can cause infections in humans. These pathogenic microbes can enter our body through the ingested food, cuts and wounds, insect bites, etc. and infect the host for their survival and reproduction. In response to the infections caused by these pathogens, our immune system gets activated to fight against them. After entering the body, pathogenic bacteria interact with the host cells and induce the production of several inflammatory molecules, sometimes this inflammation gets unbalanced or uncontrolled, leading to inflammation storms and causing severe sepsis and septic shocks1. Outer membrane proteins (OMPs) are distinctive features of Gram-negative bacteria. Apart from their structural role, they play a crucial role in host-pathogen interaction, virulence, and pathogenesis of bacteria. Upon interaction with the host immune cells, OMPs stimulate the production of proinflammatory molecules that may result in an uncontrolled inflammation, leading to severe sepsis or septic shock, which is a major cause of many deaths worldwide. A distinct group of OMPs is composed of antiparallel β-barrels connected via long loops. Several studies suggested that these surface-exposed loops interact with the host cell and participate in virulence. OMPs of Gramnegative infectious bacteria demonstrate significant conservation in the sequences, and share structural similarities within and among different species, making them useful diagnostic targets and effective vaccine candidates (Fig. 1).