Long Range Correlated Motions of TIM and their Possible Influence on Enzyme Function

Abstract

The alpha-beta barrel structure of triosephosphate isomerase (TIM) is possibly the most common among enzymes. In the case of TIM, structural dynamics are known to be essential to function. In particular the stabilization of the binding pocket by a phosphodianion “handle” of the substrate and the closing of catalytic site loops 6 and 7 over the substrate. Loop 6 moves by as much as 7 Angstroms with binding. Recently a mutant survey for human TIM (hsTIM) found kcat can change significantly for a single mutation distant from the catalytic site. Crystallographic measurements find no structural change with the mutation, suggesting a dynamical mechanism for the allosteric effect. Here we use Stationary Sample Anisotropic Terahertz Microscopy (SSATM) to measure the long-range intramolecular vibrations and determine if specific vibrations couple the allosteric and catalytic sites. SSATM isolated protein long-range structural vibrations based on the dominant displacement direction [1-4]. We examine if specific vibrational bands are associate with loop 6 and loop 7 flexibility. This work is supported by NSF grants DBI 1556359 and MCB 1616529, DOE grant DE-SC0016317 and NIH STTR R41 GM125486.1. [1]Acbas, G., K.A. Niessen, E.H. Snell, and A.G. Markelz, Nat Commun, 2014. DOI: 10.1038/ncomms4076.2. [2]Niessen, K.A., M.Y. Xu, A. Paciaroni, A. Orecchini, E.H. Snell, and A.G. Markelz, Biophys. J., 2017. DOI: 10.1016/j.bpj.2016.12.049.3. [3]Niessen, K.A. et al., Nat Commun, 2019. DOI: 10.1038/s41467-019-08926-3.4. [4]Niessen, K., Y. Deng, and A.G. Markelz, Opt. Express, 2019. DOI: 10.1364/OE.27.028036.