Adaptations for Pressure and Temperature in Dihydrofolate Reductases

Area of Science:

• Biochemistry
• Microbiology
• Structural Biology

Background:

• Extremophilic enzymes are adapted to function under harsh conditions, but pressure adaptations are complex.
• Dihydrofolate reductase (DHFR) from *Moritella profunda* (MpDHFR) shows increased activity at high pressure, potentially for cold adaptation.
• MpDHFR unfolds at ~70 MPa, while *Moritella yayanosii* (MyDHFR) originates from ~110 MPa environments, suggesting MyDHFR may be better adapted to higher pressures.

Purpose of the Study:

• To investigate the molecular adaptations of MyDHFR for high-pressure environments.
• To compare the structural stability of MyDHFR with MpDHFR under varying pressures.
• To integrate experimental data with evolutionary context and molecular dynamics simulations.

Main Methods:

• Molecular dynamics simulations of DHFR from different microbes.
• Analysis of protein structure, stability, and enzyme activity under pressure.
• Consideration of microbial evolutionary history and isolation pressures.

Main Results:

• MyDHFR exhibits adaptations for high-pressure function, unlike MpDHFR.
• A specific hydrogen bond interaction between Tyr103 (helix F) and Leu78 (helix E) in MyDHFR is identified.
• This Tyr103-Leu78 interaction in MyDHFR may prevent structural distortion at high pressures, contrasting with an intra-helix bond in MpDHFR.

Conclusions:

• MyDHFR possesses structural adaptations, particularly involving Tyr103, that confer stability at high pressures.
• The identified hydrogen bond network in MyDHFR is a key adaptation for survival in deep-sea environments.
• Understanding these adaptations provides insights into protein function under extreme conditions.