Direct visualization of critical hydrogen atoms in a pyridoxal 5'-phosphate enzyme

Dajnowicz, Steven; Johnston, Ryne C.; Parks, Jerry M.; Blakeley, Matthew P.; Keen, David A.; Weiss, Kevin L.; Gerlits, Oksana; Kovalevsky, Andrey; Mueser, Timothy C.

doi:10.1038/s41467-017-01060-y

Title: Direct visualization of critical hydrogen atoms in a pyridoxal 5'-phosphate enzyme

Journal Article · 16 October 2017 · Nature Communications

DOI: https://doi.org/10.1038/s41467-017-01060-y · OSTI ID:1407771

Dajnowicz, Steven ^[1];

^[2];

^[3];

^[4];

^[2];

^[5];

^[2]; Mueser, Timothy C. ^[6]

Univ. of Toledo, Toledo, OH (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Institut Laue Langevin, Grenoble Cedex (France)
Rutherford Appleton Lab., Didcot (United Kingdom)
Univ. of Tennessee, Knoxville, TN (United States)
Univ. of Toledo, Toledo, OH (United States)

Enzymes dependent on pyridoxal 5'-phosphate (PLP, the active form of vitamin B6) perform a myriad of diverse chemical transformations. They promote various reactions by modulating the electronic states of PLP through weak interactions in the active site. Neutron crystallography has the unique ability of visualizing the nuclear positions of hydrogen atoms in macromolecules. Here we present a room-temperature neutron structure of a homodimeric PLP-dependent enzyme, aspartate aminotransferase, which was reacted in situ with α-methylaspartate. In one monomer, the PLP remained as an internal aldimine with a deprotonated Schiff base. In the second monomer, the external aldimine formed with the substrate analog. We observe a deuterium equidistant between the Schiff base and the C-terminal carboxylate of the substrate, a position indicative of a low-barrier hydrogen bond. As a result, quantum chemical calculations and a low-pH room-temperature X-ray structure provide insight into the physical phenomena that control the electronic modulation in aspartate aminotransferase.

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Research Organization:: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: AC05-00OR22725

OSTI ID:: 1407771

Journal Information:: Nature Communications, Vol. 8, Issue 1; ISSN 2041-1723

Publisher:: Nature Publishing GroupCopyright Statement

Country of Publication:: United States

Language:: English

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