2H2N

Crystal structure of human soluble calcium-activated nucleotidase (SCAN) with calcium ion

Summary for 2H2N

• Entry DOI: 10.2210/pdb2h2n/pdb
• Related: 1S18 1S1d 2H2U
• Descriptor: Soluble calcium-activated nucleotidase 1, CALCIUM ION, ACETATE ION, ... (4 entities in total)
• Functional Keywords: nucleotidase, five-blade beta propeller, calcium-binding protein, nucleotide-binding, hydrolase
• Biological source: Homo sapiens (human)
• Cellular location: Endoplasmic reticulum membrane; Single-pass type II membrane protein: Q8WVQ1
• Total number of polymer chains: 2
• Total formula weight: 75755.27

Authors

Yang, M.,Horii, K.,Herr, A.B.,Kirley, T.L. (deposition date: 2006-05-19, release date: 2006-07-18, Last modification date: 2024-02-14)

Primary citation

Yang, M.,Horii, K.,Herr, A.B.,Kirley, T.L.
Calcium-dependent dimerization of human soluble calcium activated nucleotidase: characterization of the dimer interface.
J.Biol.Chem., 281:28307-28317, 2006

PubMed Abstract: 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.

PubMed: 16835225
DOI: 10.1074/jbc.M604413200

Experimental method

X-RAY DIFFRACTION (2.3 Å)