Abstract
Mycolyl-transferases are a family of proteins that are specifically present in the CMN (Corynebacterium, Mycobacterium and Nocardia) genera and are responsible for the synthesis of cell wall components. We modeled the three-dimensional structures of mycolyl-transfersases from Corynebacterium and Nocardia using homology modeling methods based on the crystal structures of mycolyl-transferases from M. tuberculosis. Comparison of the models revealed significant differences in their substrate binding site. Some mycolyl-transferases identified by the following Gene Ids: Nfa25110, Nfa45560, Nfa7210, Nfa38260, Nfa32420, Nfa23770, Nfa43800, Nfa30260, Dip0365, Ncgl0987, Ce1488, Ncgl0885, Ce0984, Ncgl2101, Ncgl0336, Ce0356 are associated with a relatively larger substrate binding site and amino acid residue mutations (D40N, R43D/G, S236N/A) are likely to affect binding to trehalose.
Highlights
The CMN group constitutes the organisms of the genera Corynebacterium, Mycobacterium and Nocardia, which are grouped together on the basis of factors that include complex cell wall components, presence/type of mycolic acids, adjuvant activity, presence of cord factor, sulfo-lipids, iron-chelating compounds, polyphosphate, and serological cross-reactivity
The mycolic acids are named according to the individual genus from which they are isolated; i.e., corynomycolic acids from Corynebacterium comprising ~22-36 carbons, mycolic/eumycolic acids from Mycobacterium comprising ~60-90 carbons and nocardiomycolic acids from Nocardia comprising ~40-60 carbons. [2,3,4]
It has been demonstrated that Ag85 enzymes catalyze the transfer of mycolyl residue from one molecule of α, α’ – TMM to another leading to the formation of α, α’ – TDM and these enzymes are termed mycolyl-transferases
Summary
The CMN group constitutes the organisms of the genera Corynebacterium, Mycobacterium and Nocardia, which are grouped together on the basis of factors that include complex cell wall components, presence/type of mycolic acids, adjuvant activity, presence of cord factor, sulfo-lipids, iron-chelating compounds, polyphosphate, and serological cross-reactivity. [6] in Corynebacterium and Nocardia, orthologous proteins synthesize TDCM (trehalose dicorynomycolate) and TDNM (trehalose dinocardiomycolate), respectively This family of enzymes is specific only to the CMN group of organisms because of their unique cell envelope. The structure corresponds to a α/β hydrolase fold and the catalytic triad responsible for the mycolyl-transferase activity comprise the amino acid residues S126, E230 and H262 (numbering is according to PDB Id: 1F0P). We have carried out sequence analysis corresponding to all mycolyl-transferases and modeled the structures of Nocardia and C. diphtheria and compared their substrate binding sites. Such comparative analysis is relevant in ISSN 0973-2063 Bioinformation 1(5): 161-169 (2006)
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