title: Preliminary X-ray diffraction analysis of the cytoplasmic N-terminal domain of the Na/HCO3 cotransporter NBCe1-A.
abstract: The N-terminal cytoplasmic domain of the Na+-coupled HCO_3- cotransporter NBCe1-A (NtNBCe1) has been linked with proximal renal tubular acidosis. In a previous purification study of recombinant NtNBCe1, crystal growth at a suboptimal protein concentration (<1 mg ml(-1)) yielded small single diamond-shaped crystals that diffracted poorly. In the present study, by increasing the protein concentration 50-fold, the crystal size was doubled and robustness was also improved. Crystal annealing made the crystals suitable for X-ray diffraction. The crystals either belong to space group P3(1)21 or P3(1) with pseudo P3(1)21 symmetry, with unit-cell parameters a = 51.7, b = 51.7, c = 200.6 A, alpha = beta = 90, gamma = 120 degrees , and diffract X-rays to 3.0 A resolution. The calculated Matthews number is 1.9 A3 Da(-1), with two monomers of molecular weight approximately 83 kDa in the asymmetric unit. The molecular- replacement packing solution shows that the molecules form dimers by a domain-swapping mechanism.
authors.affiliation: Department of Cellular and Molecular Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA. hs.gill@yale.edu
authors.forename: Harindarpal S
authors.initials: HS
authors.lastname: Gill
authors.forename: Walter F
authors.initials: WF
authors.lastname: Boron
mesh_terms: D003593:Cytoplasm / Q000737:chemistry; D006801:Humans; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins; D027982:Sodium-Bicarbonate Symporters / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D011994:Recombinant Proteins; D027982:Sodium-Bicarbonate Symporters