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Emergence of a novel immune-evasion strategy from an ancestral protein fold in bacteriophage mu

Karambelkar, S and Udupa, S and Gowthami, VN and Ramachandra, SG and Swapna, G and Nagaraja, V (2020) Emergence of a novel immune-evasion strategy from an ancestral protein fold in bacteriophage mu. In: Nucleic Acids Research, 48 (10). pp. 5294-5305.

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Official URL: https://doi.org/10.1093/NAR/GKAA319


The broad host range bacteriophage Mu employs a novel 'methylcarbamoyl' modification to protect its DNA from diverse restriction systems of its hosts. The DNA modification is catalyzed by a phageencoded protein Mom, whose mechanism of action is a mystery. Here, we characterized the cofactor and metal-binding properties of Mom and provide a molecular mechanism to explain 'methylcarbamoyl'ation of DNA by Mom. Computational analyses revealed a conserved GNAT (GCN5-related Nacetyltransferase) fold in Mom. We demonstrate that Mom binds to acetyl CoA and identify the active site. We discovered that Mom is an iron-binding protein, with loss of Fe2+/3+-binding associated with loss of DNA modification activity. The importance of Fe2+/3+ is highlighted by the colocalization of Fe2+/3+ with acetyl CoA within the Mom active site. Puzzlingly, acid-base mechanisms employed by >309,000 GNAT members identified so far, fail to support methylcarbamoylation of adenine using acetyl CoA. In contrast, free-radical chemistry catalyzed by transition metals like Fe2+/3+ can explain the seemingly challenging reaction, accomplished by collaboration between acetyl CoA and Fe2+/3+. Thus, binding to Fe2+/3+, a small but unprecedented step in the evolution of Mom, allows a giant chemical leap from ordinary acetylation to a novel methylcarbamoylation function, while conserving the overall protein architecture.

Item Type: Journal Article
Publication: Nucleic Acids Research
Publisher: Oxford University Press
Additional Information: The copyright for this article belongs to the Authors.
Keywords: acetyl coenzyme A; iron binding protein; membrane protein; protein Mom; unclassified drug; acetyl coenzyme A; acyltransferase; iron; Mu Mom protein, bacteriophage Mu; viral protein, Article; bacterial strain; binding affinity; controlled study; DNA modification; Enterobacteria phage Mu; Escherichia coli; gene interaction; high performance liquid chromatography; immune evasion; mass spectrometry; molecular cloning; nonhuman; protein expression; protein folding; protein function; thermostability; chemistry; Enterobacteria phage Mu; enzyme active site; genetics; metabolism; physiology; protein conformation; virology, Acetyl Coenzyme A; Acyltransferases; Bacteriophage mu; Catalytic Domain; Escherichia coli; Iron; Protein Conformation; Viral Proteins
Department/Centre: Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited: 24 Jan 2023 04:47
Last Modified: 24 Jan 2023 04:47
URI: https://eprints.iisc.ac.in/id/eprint/79303

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