PDBsum entry 6dk5

Hormone

PDB id: 6dk5

Contents

Protein chains

21 a.a.

Waters ×24

References listed in PDB file

Key reference

• Title: The X-Ray crystal structure of human endothelin 1, A polypeptide hormone regulator of blood pressure.
• Authors: A.Mcpherson, S.B.Larson.
• Ref.: Acta Crystallogr F Struct Biol Commun, 2019, 75, 47-53. [DOI no: 10.1107/S2053230X18016011]
• PubMed id: 30605125

Abstract

Human endothelin is a 21-amino-acid polypeptide, constrained by two intra-chain disulfide bridges, that is made by endothelial cells. It is the most potent vasoconstrictor in the body and is crucially important in the regulation of blood pressure. It plays a major role in a host of medical conditions, including hypertension, diabetes, stroke and cancer. Endothelin was crystallized 28 years ago in the putative space group P6₁22, but the structure was never successfully solved by X-ray diffraction. Using X-ray diffraction data from 1992, the structure has now been solved. Assuming a unit cell belonging to space group P6₁ and a twin fraction of 0.28, a solution emerged with two, almost identical, closely associated molecules in the asymmetric unit. Although the data extended to beyond 1.8 Å resolution, a model containing 25 waters was refined to 1.85 Å resolution with an R of 0.216 and an R_free of 0.284. The disulfide-constrained `core' of the molecule, amino-acid residues 1-15, has a main-chain conformation that is essentially the same as endothelin when bound to its receptor, but many side-chain rotamers are different. The carboxy-terminal `tail' comprising amino-acid residues 16-21 is extended as when receptor-bound, but it exhibits a different conformation with respect to the `core'. The dimer that comprises the asymmetric unit is maintained almost exclusively by hydrophobic interactions and may be stable in an aqueous medium.