Predicted molecular structure of the mammalian cell entry protein Mce1A of Mycobacterium tuberculosis.
The proposed role of the mammalian cell entry protein 1A (Mce1A) of Mycobacterium tuberculosis is to facilitate invasion of host cells. The structure of Mce1A was modelled on the basis of the crystal structure of Colicin N of Escherichia coli by fold prediction and threading. Mce1A, as the model predicts, is an alpha/beta protein consisting of two major (alpha and beta) domains, connected by a long alpha helix. The model further revealed that the protein contains 12 helices, 9 strands, and 1 turn. The final model of Mce1A was verified through the program VERIFY 3D and more than 90% of the residues were in the favourable region. A mouse monoclonal antibody, TB1-5 76C, is directed to an epitope within a 60-mer peptide that has been shown to promote uptake of bacteria in mammalian cells. We show here that the epitope could be narrowed down to a core of 4 amino acids, TPKD. Upstream flanking residues, KRR also contributed to binding. Mce2A does not promote uptake in mammalian cells and sequence comparison of Mce1A and Mce2A indicates that the epitope mediates uptake. The epitope was located at the surface of the Mce1A model at the distal beta strand-loop region in the beta domain. The localization of this epitope in the model confirms its potential role in promoting uptake of M. tuberculosis in host cells.
Das
Amit Kumar
AK
Department of Biotechnology, Indian Institute of Technology, Kharagpur 721 302, West Bengal, India.
Mitra
Devrani
D
Harboe
Morten
M
Nandi
Bidisha
B
Harkness
Robin E
RE
Das
Debabrata
D
Wiker
Harald G
HG
D000465:Algorithms; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000737:chemistry*; D003087:Colicins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D019992:Databases as Topic; D004797:Enzyme-Linked Immunosorbent Assay; D000939:Epitopes; D004926:Escherichia coli / Q000378:metabolism; D007930:Leucine / Q000737:chemistry; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000378:metabolism*; D010452:Peptide Biosynthesis; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D003087:Colicins; D000939:Epitopes; D010455:Peptides; C473802:mammalian cell entry protein Mce1A, Mycobacterium tuberculosis; D007930:Leucine