Structure function studies on truncated hemoglobins of Mycobacterium smegmatis

Abstract

Truncated hemoglobins (trHbs) are a distinct class of proteins found in bacteria, lower eukaryotes, and plants. Although their exact functions are not fully understood, studies have primarily focused on pathogenic mycobacteria such as Mycobacterium tuberculosis (Mtb) and Mycobacterium leprae. These studies have revealed that trHbs play various roles in the cellular metabolism of their hosts, including oxygen metabolism, scavenging reactive nitrogen and oxygen species, and host-pathogen interactions.In this study, trHbs (Ms.HbO and Ms.HbN) in non-pathogenic, fast-growing mycobacteria.i.e M. smegmatis. were investigated. These two trHbs, Ms.HbO and Ms.HbN, in M. smegmatis showed significant sequence similarity to trHbO and trHbN in Mtb. The genes encoding Ms.HbO and Ms.HbN were cloned and overexpressed in both E. coli and M. smegmatis to gain insights into their physiological roles. Transcript analysis of the genes encoding Ms.HbO and Ms.HbN suggested their involvement in supporting cellular metabolism under low oxygen and oxidative stress. The proteins were also found to affect the composition of the bacterial cell wall, promoting biofilm formation and conferring resistance to various stresses. Moreover, overexpression of these genes influenced the immune responses and enhanced the survival of M. smegmatis during macrophage infection. The similarities between trHbO and trHbN in M. smegmatis and Mtb suggest that the findings from this study may provide valuable insights into the functions of these proteins in pathogenic mycobacteria. Further research is needed to uncover the molecular mechanisms by which trHbO and trHbN modulate cell survival and the expression of inflammatory cytokines during intracellular infection. newline