[SCAN] Unraveling the haem biosynthesis pathway in the Gram-negative pathogen Campylobacter jejuni

Title: Unraveling the haem biosynthesis pathway in the Gram-negative pathogen Campylobacter jejuni

Speaker: Jordi Zamarreno

Abstract: Campylobacter jejuni is the major cause of gastroenteritis in the world and responsible for ~1/4 of diarrhoeal diseases in the world. Despite the increasing number of infections caused by C. jejuni, the molecular mechanisms involved in pathogen’s survival within the host are still poorly understood. Haem biosynthesis plays a crucial role in pathogen´s physiology as it ensures the formation of several essential haem-binding proteins/enzymes. Indeed, haem cofactor is responsible for the function of several key cellular processes such as, respiration, signaling and oxidative stress detoxification. Therefore, most prokaryotes, synthesize haem endogenously via specific Haem Synthesis Pathways (HSP). All the so far known HSP begin with the universal tetrapyrrole precursor δ-aminolaevulinic acid (ALA) and uses a cascade of enzymes to finally produce haem. The best-known pathway, currently named the protoporphyrin dependent pathway (PPD), involves at least eight enzymes to go from ALA to haem and is mostly present in Gram-negative bacteria. Our group participated in the discovery of two other distinct pathways, namely the sirohaem dependent pathway and the coproporphyrin dependent pathway. That are present mainly in sulphate-reducing bacteria and Gram-positive pathogens, respectively.
We described our data on the elucidation of which pathway does C. jejuni uses to synthesise haem.  We performed the biochemical characterization of the enzymes involved in this pathway. Moreover, we show results on the identification of a novel putative haem chaperon encoded in C. jejuni.