Issue 8, 2016

The unique functional role of the C–H⋯S hydrogen bond in the substrate specificity and enzyme catalysis of type 1 methionine aminopeptidase

Abstract

It is intriguing how nature attains recognition specificity between molecular interfaces where there is no apparent scope for classical hydrogen bonding or polar interactions. Methionine aminopeptidase (MetAP) is one such enzyme where this fascinating conundrum is at play. In this study, we demonstrate that a unique C–H⋯S hydrogen bond exists between the enzyme methionine aminopeptidase (MetAP) and its N-terminal-methionine polypeptide substrate, which allows specific interaction between apparent apolar interfaces, imposing a strict substrate recognition specificity and efficient catalysis, a feature replicated in Type I MetAPs across all kingdoms of life. We evidence this evolutionarily conserved C–H⋯S hydrogen bond through enzyme assays on wild-type and mutant MetAP proteins from Mycobacterium tuberculosis that show a drastic difference in catalytic efficiency. The X-ray crystallographic structure of the methionine bound protein revealed a conserved water bridge and short contacts involving the Met side-chain, a feature also observed in MetAPs from other organisms. Thermal shift assays showed a remarkable 3.3 °C increase in melting temperature for methionine bound protein compared to its norleucine homolog, where C–H⋯S interaction is absent. The presence of C–H⋯S hydrogen bonding was also corroborated by nuclear magnetic resonance spectroscopy through a change in chemical shift. Computational chemistry studies revealed the unique role of the electrostatic environment in facilitating the C–H⋯S interaction. The significance of this atypical hydrogen bond is underscored by the fact that the function of MetAP is essential for any living cell.

Graphical abstract: The unique functional role of the C–H⋯S hydrogen bond in the substrate specificity and enzyme catalysis of type 1 methionine aminopeptidase

Supplementary files

Article information

Article type
Paper
Submitted
06 Apr 2016
Accepted
11 Mei 2016
First published
12 Mei 2016

Mol. BioSyst., 2016,12, 2408-2416

The unique functional role of the C–H⋯S hydrogen bond in the substrate specificity and enzyme catalysis of type 1 methionine aminopeptidase

R. Reddi, K. K. Singarapu, D. Pal and A. Addlagatta, Mol. BioSyst., 2016, 12, 2408 DOI: 10.1039/C6MB00259E

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Spotlight

Advertisements