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| {{STRUCTURE_2h2n| PDB=2h2n | SCENE= }} | | {{STRUCTURE_2h2n| PDB=2h2n | SCENE= }} |
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| '''Crystal structure of human soluble calcium-activated nucleotidase (SCAN) with calcium ion'''
| | ===Crystal structure of human soluble calcium-activated nucleotidase (SCAN) with calcium ion=== |
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| ==Overview==
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| Mammals express a protein homologous to soluble nucleotidases used by blood-sucking insects to inhibit host blood clotting. These vertebrate nucleotidases may play a role in protein glycosylation. The activity of this enzyme family is strictly dependent on calcium, which induces a conformational change in the secreted, soluble human nucleotidase. The crystal structure of this human enzyme was recently solved; however, the mechanism of calcium activation and the basis for the calcium-induced changes remain unclear. In this study, using analytical ultracentrifugation and chemical cross-linking, we show that calcium or strontium induce noncovalent dimerization of the soluble human enzyme. The location and nature of the dimer interface was elucidated using a combination of site-directed mutagenesis and chemical cross-linking, coupled with crystallographic analyses. Replacement of Ile(170), Ser(172), and Ser(226) with cysteine residues resulted in calcium-dependent, sulfhydryl-specific intermolecular cross-linking, which was not observed after cysteine introduction at other surface locations. Analysis of a super-active mutant, E130Y, revealed that this mutant dimerized more readily than the wild-type enzyme. The crystal structure of the E130Y mutant revealed that the mutated residue is found in the dimer interface. In addition, expression of the full-length nucleotidase revealed that this membrane-bound form can also dimerize and that these dimers are stabilized by spontaneous oxidative cross-linking of Cys(30), located between the single transmembrane helix and the start of the soluble sequence. Thus, calcium-mediated dimerization may also represent a mechanism for regulation of the activity of this nucleotidase in the physiological setting of the endoplasmic reticulum or Golgi.
| | The line below this paragraph, {{ABSTRACT_PUBMED_16835225}}, adds the Publication Abstract to the page |
| | (as it appears on PubMed at http://www.pubmed.gov), where 16835225 is the PubMed ID number. |
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| | {{ABSTRACT_PUBMED_16835225}} |
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| ==About this Structure== | | ==About this Structure== |
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| [[Category: Nucleotidase]] | | [[Category: Nucleotidase]] |
| [[Category: Nucleotide-binding]] | | [[Category: Nucleotide-binding]] |
| ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun May 4 05:47:55 2008'' | | |
| | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Tue Jul 29 11:12:21 2008'' |
