Metalloprotein entatic control of ligand-metal bonds quantified by ultrafast x-ray spectroscopy

Michael William Mara, Ryan G. Hadt, Marco Eli Reinhard, Thomas Kroll, Hyeongtaek Lim, Robert W. Hartsock, Roberto Alonso-Mori, Matthieu Chollet, James M. Glownia, Silke Nelson, Dimosthenis Sokaras, Kristjan Kunnus, Keith O. Hodgson, Britt Hedman, Uwe Bergmann, Kelly J. Gaffney, Edward I. Solomon*

*Corresponding author for this work

Research output: Contribution to journalArticle

57 Scopus citations

Abstract

The multifunctional protein cytochrome c (cyt c) plays key roles in electron transport and apoptosis, switching function by modulating bonding between a heme iron and the sulfur in a methionine residue. This Fe-S(Met) bond is too weak to persist in the absence of protein constraints.We ruptured the bond in ferrous cyt c using an optical laser pulse and monitored the bond reformation within the protein active site using ultrafast x-ray pulses from an x-ray free-electron laser, determining that the Fe-S(Met) bond enthalpy is ∼4 kcal/mol stronger than in the absence of protein constraints.The 4 kcal/mol is comparable with calculations of stabilization effects in other systems, demonstrating how biological systems use an entatic state for modest yet accessible energetics to modulate chemical function.

Original languageEnglish (US)
Pages (from-to)1276-1280
Number of pages5
JournalScience
Volume356
Issue number6344
DOIs
StatePublished - Jun 23 2017

ASJC Scopus subject areas

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    Mara, M. W., Hadt, R. G., Reinhard, M. E., Kroll, T., Lim, H., Hartsock, R. W., Alonso-Mori, R., Chollet, M., Glownia, J. M., Nelson, S., Sokaras, D., Kunnus, K., Hodgson, K. O., Hedman, B., Bergmann, U., Gaffney, K. J., & Solomon, E. I. (2017). Metalloprotein entatic control of ligand-metal bonds quantified by ultrafast x-ray spectroscopy. Science, 356(6344), 1276-1280. https://doi.org/10.1126/science.aam6203