6dk5: Difference between revisions

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== Publication Abstract from PubMed ==
== Publication Abstract from PubMed ==
Human apolipoprotein C1 (APOC1) is a 57 amino acid long polypeptide that through its potent inhibition of cholesterol ester transferase protein helps regulate the transfer of lipids between lipid particles. We have now determined the structure of APOC1 in four crystal forms by X-ray diffraction. A molecule of APOC1 is a single, slightly bent, alpha helix having 13 to 14 turns and a length of about 80 A. APOC1 exists as a dimer, but the dimers are not the same in the four crystals. In two monoclinic crystals, two helices closely engage one another in an anti-parallel fashion. The interactions between monomers are almost entirely hydrophobic with sparse electrostatic complements. In the third monoclinic crystal, the two monomers spread at one end of the dimer, like a scissor opening, and by translation along the crystallographic a axis, form a continuous, contiguous, sheet through the crystal. In the orthorhombic crystals two molecules of APOC1 are related by a non-crystallographic twofold axis to create an arc of about 120 A length. This symmetrical dimer utilizes interactions not present in dimers of the monoclinic crystals. Versatility of APOC1 monomer association shown by these crystals is suggestive of physiological function.
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 A resolution, a model containing 25 waters was refined to 1.85 A resolution with an R of 0.216 and an Rfree 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.


The Structure of Human Apolipoprotein C-1 in Four Different Crystal Forms.,McPherson A, Larson SB J Lipid Res. 2018 Dec 17. pii: jlr.M089441. doi: 10.1194/jlr.M089441. PMID:30559175<ref>PMID:30559175</ref>
The X-ray crystal structure of human endothelin 1, a polypeptide hormone regulator of blood pressure.,McPherson A, Larson SB Acta Crystallogr F Struct Biol Commun. 2019 Jan 1;75(Pt 1):47-53. doi:, 10.1107/S2053230X18016011. Epub 2019 Jan 1. PMID:30605125<ref>PMID:30605125</ref>


From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

Revision as of 15:30, 16 January 2019

The X-ray crystal structure of human endothelin-1, a polypeptide hormone regulator of blood pressureThe X-ray crystal structure of human endothelin-1, a polypeptide hormone regulator of blood pressure

Structural highlights

6dk5 is a 2 chain structure with sequence from Homo sapiens. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance.
Resources:FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT

Function

[EDN1_HUMAN] Endothelins are endothelium-derived vasoconstrictor peptides.

Publication Abstract from PubMed

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 A resolution, a model containing 25 waters was refined to 1.85 A resolution with an R of 0.216 and an Rfree 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.

The X-ray crystal structure of human endothelin 1, a polypeptide hormone regulator of blood pressure.,McPherson A, Larson SB Acta Crystallogr F Struct Biol Commun. 2019 Jan 1;75(Pt 1):47-53. doi:, 10.1107/S2053230X18016011. Epub 2019 Jan 1. PMID:30605125[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

References

  1. McPherson A, Larson SB. The X-ray crystal structure of human endothelin 1, a polypeptide hormone regulator of blood pressure. Acta Crystallogr F Struct Biol Commun. 2019 Jan 1;75(Pt 1):47-53. doi:, 10.1107/S2053230X18016011. Epub 2019 Jan 1. PMID:30605125 doi:http://dx.doi.org/10.1107/S2053230X18016011

6dk5, resolution 1.85Å

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OCA