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A 3.3?A-Resolution Structure of Hyperthermophilic Respiratory Complex?III Reveals the Mechanism of Its Thermal Stability.

ABSTRACT: Respiratory chain complexes convert energy by coupling electron flow to transmembrane proton translocation. Owing to a lack of atomic structures of cytochrome?bc1 complex (Complex?III) from thermophilic bacteria, little is known about the adaptations of this macromolecular machine to hyperthermophilic environments. In this study, we purified the cytochrome?bc1 complex of Aquifex aeolicus, one of the most extreme thermophilic bacteria known, and determined its structure with and without an inhibitor at 3.3?Å resolution. Several residues unique for thermophilic bacteria were detected that provide additional stabilization for the structure. An extra transmembrane helix at the N-terminus of cyt.?c1 was found to greatly enhance the interaction between cyt.?b and cyt.?c1 , and to bind a phospholipid molecule to stabilize the complex in the membrane. These results provide the structural basis for the hyperstability of the cytochrome?bc1 complex in an extreme thermal environment.

SUBMITTER: Zhu G

PROVIDER: S-EPMC7004027 | biostudies-literature | 2020 Jan

REPOSITORIES: biostudies-literature

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A 3.3 Å-Resolution Structure of Hyperthermophilic Respiratory Complex III Reveals the Mechanism of Its Thermal Stability.

Zhu Guoliang G Zeng Hui H Zhang Shuangbo S Juli Jana J Pang Xiaoyun X Hoffmann Jan J Zhang Yan Y Morgner Nina N Zhu Yun Y Peng Guohong G Michel Hartmut H Sun Fei F

Angewandte Chemie (International ed. in English) 20191128 1

Respiratory chain complexes convert energy by coupling electron flow to transmembrane proton translocation. Owing to a lack of atomic structures of cytochrome bc<sub>1</sub> complex (Complex III) from thermophilic bacteria, little is known about the adaptations of this macromolecular machine to hyperthermophilic environments. In this study, we purified the cytochrome bc<sub>1</sub> complex of Aquifex aeolicus, one of the most extreme thermophilic bacteria known, and determined its structure with ...[more]

PMID: 31778296

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Project description:Hydrophobic interactions and hydrogen bonds are 2 types of noncovalent interactions that play distinct roles in the folding and structural stability of proteins. However, the specific roles of these interactions in hydrophobic or hydrophilic environments in α/β-hydrolases are not fully understood. A hyperthermophilic esterase EstE1 in a dimer maintains the C-terminal β8-α9 strand-helix via hydrophobic interactions (Phe276 and Leu299), constituting a closed dimer interface. Moreover, a mesophilic esterase rPPE in a monomer maintains the same strand-helix via a hydrogen bond (Tyr281 and Gln306). Unpaired polar residues (F276Y in EstE1 and Y281A/F and Q306A in rPPE) or reduced hydrophobic interactions (F276A/L299A in EstE1) between the β8-α9 strand-helix decrease thermal stability. EstE1 (F276Y/L299Q) and rPPE WT, both with the β8-α9 hydrogen bond, showed the same thermal stability as EstE1 WT and rPPE (Y281F/Q306L), which possess hydrophobic interactions instead. However, EstE1 (F276Y/L299Q) and rPPE WT exhibited higher enzymatic activity than EstE1 WT and rPPE (Y281F/Q306L), respectively. This suggests that α/β-hydrolases favor the β8-α9 hydrogen bond for catalytic activity in monomers or oligomers. Overall, these findings demonstrate how α/β-hydrolases modulate hydrophobic interactions and hydrogen bonds to adapt to different environments. Both types of interactions contribute equally to thermal stability, but the hydrogen bond is preferred for catalytic activity. IMPORTANCE Esterases hydrolyze short to medium-chain monoesters and contain a catalytic His on a loop between the C-terminal β8-strand and α9-helix. This study explores how hyperthermophilic esterase EstE1 and mesophilic esterase rPPE adapt to different temperatures by utilizing the β8-α9 hydrogen bonds or hydrophobic interactions differently. EstE1 forms a hydrophobic dimer interface, while rPPE forms a monomer stabilized by a hydrogen bond. The study demonstrates that these enzymes stabilize β8-α9 strand-helix differently but achieve similar thermal stability. While the β8-α9 hydrogen bond or hydrophobic interactions contribute equally to thermal stability, the hydrogen bond provides higher activity due to increased catalytic His loop flexibility in both EstE1 and rPPE. These findings reveal how enzymes adapt to extreme environments while maintaining their functions and have implications for engineering enzymes with desired activities and stabilities.

Dataset Information

A 3.3?A-Resolution Structure of Hyperthermophilic Respiratory Complex?III Reveals the Mechanism of Its Thermal Stability.

Publications

A 3.3 Å-Resolution Structure of Hyperthermophilic Respiratory Complex III Reveals the Mechanism of Its Thermal Stability.

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