Inter-Domain Hydrophobic Interactions Modulate the Thermostability of Microbial Esterases from the Hormone-Sensitive Lipase Family [Enzymology]

March 14th, 2015 by Li, P.-Y., Chen, X.-L., Ji, P., Li, C.-Y., Wang, P., Zhang, Y., Xie, B.-B., Qin, Q.-L., Su, H.-N., Zhou, B.-C., Zhang, Y.-Z., Zhang, X.-Y.

Microbial hormone-sensitive lipases (HSLs) contain a CAP domain and a catalytic domain. However, it remains unclear how the CAP domain interacts with the catalytic domain to maintain the stability of microbial HSLs. Here, we isolated an HSL esterase, E40, from a marine sedimental metagenomic library. E40 exhibited the maximal activity at 45°C, and was quite thermolabile, with a half life of only 2 min at 40°C, which may be an adaptation of E40 to the permanently cold sediment environment. The structure of E40 was solved to study its thermolability. Structural analysis showed that E40 lacks the inter-domain hydrophobic interactions between the loop1 of the CAP domain and the α7 of the catalytic domain compared to its thermostable homologs. Mutational analysis showed that, the introduction of hydrophobic residues Trp202 and Phe203 in the α7 significantly improved E40 stability, and that a further introduction of hydrophobic residues in the loop1 made E40 more thermostable due to the formation of inter-domain hydrophobic interactions. Altogether, the results indicate that the absence of inter-domain hydrophobic interactions between the loop1 and the α7 leads to the thermolability of E40. In addition, a comparative analysis of the structures of E40 and other thermolabile and thermostable HSLs suggests that the inter-domain hydrophobic interactions between the loop1 and the α7 are a key element for the thermostability of microbial HSLs. Therefore, this study not only illustrates the structural element leading to the thermolability of E40, but also reveals a structural determinant for HSL thermostability.
  • Posted in Journal of Biological Chemistry, Publications
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