Structural Characterization of an ACP from <i>Thermotoga maritima</i>: Insights into Hyperthermal Adaptation

• Main Authors: Yeongjoon Lee, Ahjin Jang, Min-Cheol Jeong, Nuri Park, Jungwoo Park, Woo Cheol Lee, Chaejoon Cheong, Yangmee Kim
• Format: Article
• Language: English
• Published: MDPI AG 2020-04-01
• Series: International Journal of Molecular Sciences
• Subjects: Acyl carrier protein; NMR spectroscopy; structure; thermostability; <i>Thermotoga maritima</i>
• Online Access: https://www.mdpi.com/1422-0067/21/7/2600
• ISSN: 1661-6596; 1422-0067

<i>Thermotoga maritima</i>, a deep-branching hyperthermophilic bacterium, expresses an extraordinarily stable <i>Thermotoga maritima</i> acyl carrier protein (<i>Tm</i>-ACP) that functions as a carrier in the fatty acid synthesis system at near-boiling aqueous environments. Here, to understand the hyperthermal adaptation of <i>Tm</i>-ACP, we investigated the structure and dynamics of <i>Tm</i>-ACP by nuclear magnetic resonance (NMR) spectroscopy. The melting temperature of <i>Tm</i>-ACP (101.4 °C) far exceeds that of other ACPs, owing to extensive ionic interactions and tight hydrophobic packing. The D59 residue, which replaces Pro/Ser of other ACPs, mediates ionic clustering between helices III and IV. This creates a wide pocket entrance to facilitate the accommodation of long acyl chains required for hyperthermal adaptation of the <i>T. maritima</i> cell membrane. <i>Tm</i>-ACP is revealed to be the first ACP that harbor an amide proton hyperprotected against hydrogen/deuterium exchange for I15. The hydrophobic interactions mediated by I15 appear to be the key driving forces of the global folding process of <i>Tm</i>-ACP. Our findings provide insights into the structural basis of the hyperthermal adaptation of ACP, which might have allowed <i>T. maritima</i> to survive in hot ancient oceans.