title: A structural and functional investigation of a novel protein from Mycobacterium smegmatis implicated in mycobacterial macrophage survivability.
abstract: The success of pathogenic mycobacterial species is owing in part to their ability to parasitize the generally inhospitable phagosomal environment of host macrophages, utilizing a variety of strategies to avoid their antimycobacterial capabilities and thereby enabling their survival. A recently identified gene target in Mycobacterium smegmatis, highly conserved within Mycobacterium spp. and denoted MSMEG_5817, has been found to be important for bacterial survival within host macrophages. To gain insight into its function, the crystal structure of MSMEG_5817 has been solved to 2.40 Å resolution. The structure reveals a high level of structural homology to the sterol carrier protein (SCP) family, suggesting a potential role of MSMEG_5817 in the binding and transportation of biologically relevant lipids required for bacterial survival. The lipid-binding capacity of MSMEG_5817 was confirmed by ELISA, revealing binding to a number of phospholipids with varying binding specificities compared with Homo sapiens SCP. A potential lipid-binding site was probed by alanine-scanning mutagenesis, revealing structurally relevant residues and a binding mechanism potentially differing from that of the SCPs.
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Adam
authors.initials: A
authors.lastname: Shahine
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Dene
authors.initials: D
authors.lastname: Littler
authors.affiliation: Australian Research Council (ARC) Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Rajini
authors.initials: R
authors.lastname: Brammananath
authors.affiliation: Australian Research Council (ARC) Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Phooi Y
authors.initials: PY
authors.lastname: Chan
authors.affiliation: Australian Research Council (ARC) Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Paul K
authors.initials: PK
authors.lastname: Crellin
authors.affiliation: Australian Research Council (ARC) Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Ross L
authors.initials: RL
authors.lastname: Coppel
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Jamie
authors.initials: J
authors.lastname: Rossjohn
authors.affiliation: Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria 3800, Australia.
authors.forename: Travis
authors.initials: T
authors.lastname: Beddoe
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000502:physiology; D002942:Circular Dichroism; D003461:Crystallography; D004797:Enzyme-Linked Immunosorbent Assay; D008264:Macrophages / Q000276:immunology / Q000382:microbiology*; D020102:Mycobacterium smegmatis / Q000737:chemistry* / Q000472:pathogenicity; D016133:Polymerase Chain Reaction; D011487:Protein Conformation
chemical_list: D001426:Bacterial Proteins
keywords: MSMEG_5817; Mycobacterium smegmatis; PI3P; selenomethionine; sterol carrier protein