title: Lipoprotein LprI of Mycobacterium tuberculosis Acts as a Lysozyme Inhibitor.
abstract: Mycobacterium tuberculosis executes numerous defense strategies for the successful establishment of infection under a diverse array of challenges inside the host. One such strategy that has been delineated in this study is the abrogation of lytic activity of lysozyme by a novel glycosylated and surface-localized lipoprotein, LprI, which is exclusively present in M. tuberculosis complex. The lprI gene co-transcribes with the glbN gene (encoding hemoglobin (HbN)) and both are synchronously up-regulated in M. tuberculosis during macrophage infection. Recombinant LprI, expressed in Escherichia coli, exhibited strong binding (Kd ≤ 2 nm) with lysozyme and abrogated its lytic activity completely, thereby conferring protection to fluorescein-labeled Micrococcus lysodeikticus from lysozyme-mediated hydrolysis. Expression of the lprI gene in Mycobacterium smegmatis (8-10-fold) protected its growth from lysozyme inhibition in vitro and enhanced its phagocytosis and survival during intracellular infection of peritoneal and monocyte-derived macrophages, known to secrete lysozyme, and in the presence of exogenously added lysozyme in secondary cell lines where lysozyme levels are low. In contrast, the presence of HbN enhanced phagocytosis and intracellular survival of M. smegmatis only in the absence of lysozyme but not under lysozyme stress. Interestingly, co-expression of the glbN-lprI gene pair elevated the invasion and survival of M. smegmatis 2-3-fold in secondary cell lines in the presence of lysozyme in comparison with isogenic cells expressing these genes individually. Thus, specific advantage against macrophage-generated lysozyme, conferred by the combination of LprI-HbN during invasion of M. tuberculosis, may have vital implications on the pathogenesis of tuberculosis.
authors.affiliation: From the Council of Scientific and Industrial Research-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India.
authors.forename: Deepti
authors.initials: D
authors.lastname: Sethi
authors.affiliation: From the Council of Scientific and Industrial Research-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India.
authors.forename: Sahil
authors.initials: S
authors.lastname: Mahajan
authors.affiliation: From the Council of Scientific and Industrial Research-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India.
authors.forename: Chaahat
authors.initials: C
authors.lastname: Singh
authors.affiliation: From the Council of Scientific and Industrial Research-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India.
authors.forename: Amrita
authors.initials: A
authors.lastname: Lama
authors.affiliation: From the Council of Scientific and Industrial Research-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India.
authors.forename: Mangesh Dattu
authors.initials: MD
authors.lastname: Hade
authors.affiliation: From the Council of Scientific and Industrial Research-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India.
authors.forename: Pawan
authors.initials: P
authors.lastname: Gupta
authors.affiliation: From the Council of Scientific and Industrial Research-Institute of Microbial Technology, Sector 39A, Chandigarh 160036, India kanak@imtech.res.in.
authors.forename: Kanak L
authors.initials: KL
authors.lastname: Dikshit
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism*; D008074:Lipoproteins / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D008264:Macrophages / Q000737:chemistry / Q000378:metabolism / Q000382:microbiology* / Q000473:pathology; D051379:Mice; D009113:Muramidase / Q000037:antagonists & inhibitors*; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D008074:Lipoproteins; D011994:Recombinant Proteins; D009113:Muramidase
keywords: bacterial pathogenesis; hemoglobin; lipoprotein; microbiology; molecular biology