Adaptations for Pressure and Temperature in Dihydrofolate Reductases.

Ryan W Penhallurick,Alliyah Harold,Maya D Durnal,Toshiko Ichiye

doi:10.3390/microorganisms9081706

Ryan W Penhallurick, Alliyah Harold + Show 2 more

Open Access

https://doi.org/10.3390/microorganisms9081706

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Journal: Microorganisms	Publication Date: Aug 11, 2021
Citations: 3	License type: CC BY 4.0

Affiliation: Georgetown University

Abstract

Enzymes from extremophilic microbes that live in extreme conditions are generally adapted so that they function under those conditions, although adaptations for extreme temperatures and pressures can be difficult to unravel. Previous studies have shown mutation of Asp27 in Escherichia coli dihydrofolate reductase (DHFR) to Glu27 in Moritella profunda (Mp). DHFR enhances activity at higher pressures, although this may be an adaptation for cold. Interestingly, MpDHFR unfolds at ~70 MPa, while Moritella yayanosii (My) was isolated at depths corresponding to ~110 MPa, indicating that MyDHFR might be adapted for higher pressures. Here, these adaptations are examined using molecular dynamics simulations of DHFR from different microbes in the context of not only experimental studies of activity and stability of the protein but also the evolutionary history of the microbe. Results suggest Tyr103 of MyDHFR may be an adaptation for high pressure since Cys103 in helix F of MpDHFR forms an intra-helix hydrogen bond with Ile99 while Tyr103 in helix F of MyDHFR forms a hydrogen bond with Leu78 in helix E. This suggests the hydrogen bond between helices F and E in MyDHFR might prevent distortion at higher pressures.

Highlights

The discoveries of “extremophilic” organisms that thrive under extremes of temperature, pressure, and other conditions [1] raise questions about the nature of adaptations in their biomolecules so that they can function under conditions where their counterparts from mesophiles would fail
Psychrophilic microbes have been found growing at temperatures as low as −20 ◦ C [3], while thermophilic microbes can grow at temperatures as high as 122 ◦ C [4]
When comparing hydrogen bonds with greater than 50% occupancy in the simulations at 1 bar, 87 appear to be common between EcDHFR and D27E EcDHFR, 84 are common between MpDHFR and MyDHFR, and most of these are common between all 4 dihydrofolate reductase (DHFR)

Summary

Introduction

Consistent with the hypothesis that enzyme activity is similar at “corresponding states” of their microbial source, namely, the growth temperature TG of the microbe [5,6], homologous enzymes from psychrophiles, mesophiles, and thermophiles, often have maximum activity near the TG of the microbes [7,8]. Enzymes from thermophiles apparently need more stabilizing interactions so that they do not unfold at the high TG of their organism, while enzymes from psychrophiles often have fewer stabilizing interactions, which have been suggested to promote flexibility for activity at the low TG of their organism. A balance between stability and flexibility might be necessary since more interactions promote stability while fewer interactions microorganisms9081706. Microorganisms 2021, 9, 1706 promote flexibility, giving rise to the maximum activity near TG [7].

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