title: Biochemical evidence for relaxed substrate specificity of Nα-acetyltransferase (Rv3420c/rimI) of Mycobacterium tuberculosis.
abstract: Nα-acetylation is a naturally occurring irreversible modification of N-termini of proteins catalyzed by Nα-acetyltransferases (NATs). Although present in all three domains of life, it is little understood in bacteria. The functional grouping of NATs into six types NatA - NatF, in eukaryotes is based on subunit requirements and stringent substrate specificities. Bacterial orthologs are phylogenetically divergent from eukaryotic NATs, and only a couple of them are characterized biochemically. Accordingly, not much is known about their substrate specificities. Rv3420c of Mycobacterium tuberculosis is a NAT ortholog coding for RimI(Mtb). Using in vitro peptide-based enzyme assays and mass-spectrometry methods, we provide evidence that RimI(Mtb) is a protein Nα-acetyltransferase of relaxed substrate specificity mimicking substrate specificities of eukaryotic NatA, NatC and most competently that of NatE. Also, hitherto unknown acetylation of residues namely, Asp, Glu, Tyr and Leu by a bacterial NAT (RimI(Mtb)) is elucidated, in vitro. Based on in vivo acetylation status, in vitro assay results and genetic context, a plausible cellular substrate for RimI(Mtb) is proposed.
authors.affiliation: CSIR-Institute of Microbial Technology, Sector 39-A, Chandigarh, 160036, India.
authors.forename: Deepika
authors.initials: D
authors.lastname: Pathak
authors.affiliation: CSIR-Institute of Microbial Technology, Sector 39-A, Chandigarh, 160036, India.
authors.forename: Aadil Hussain
authors.initials: AH
authors.lastname: Bhat
authors.affiliation: CSIR-Institute of Microbial Technology, Sector 39-A, Chandigarh, 160036, India.
authors.forename: Vandana
authors.initials: V
authors.lastname: Sapehia
authors.affiliation: Institute of Forensic Science &Criminology, Panjab University, Sector 14, Chandigarh, 160014, India.
authors.forename: Jagdish
authors.initials: J
authors.lastname: Rai
authors.affiliation: CSIR-Institute of Microbial Technology, Sector 39-A, Chandigarh, 160036, India.
authors.forename: Alka
authors.initials: A
authors.lastname: Rao
mesh_terms: D000107:Acetylation; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D020134:Catalytic Domain; D008958:Models, Molecular; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D063206:N-Terminal Acetyltransferases / Q000737:chemistry*; D010446:Peptide Fragments / Q000737:chemistry; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D020836:Protein Structure, Quaternary; D012996:Solutions; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D010446:Peptide Fragments; D012996:Solutions; D063206:N-Terminal Acetyltransferases