Schueler C , Becker HM , McKenna R , Deitmer JW .

	Figure 1. Fluorescent staining of CA isoforms and mutants.Optical slices of oocytes, labeled via primary antibodies and Alexa Fluor 488-linked secondary antibodies against CAI (A), CAII (B), CAIII (C), CAII-Y7F (D), -H64A (E) and -V143Y-expressing oocytes (F). As control, a staining of native, uninjected oocytes or oocytes injected with H2O with primary antibodies against CAI (G), CAII (H) and CAIII (I) as well as corresponding secondary antibodies, respectively, was performed.
	Figure 2. Activity of CAI, II and III.Original recordings of changes of intracellular proton concentration (ΔH+; A) and statistical analysis of the rates of rise of proton concentration (ΔH+/t; B) after application of 5% CO2/24 mM HCO3−-buffered solution before or during application of EZA (10 µM). The asterisks above the bars correspond to the control cells without CA (−CA) before (−EZA) or during application of EZA (+EZA). (C) Original recordings of the log enrichment of 20 oocytes expressing CAI, CAII and CAIII, respectively, either alone or together with the NBCe1, or 20 CAII-V143Y, native or just NBCe1-expressing oocytes as measured by mass spectrometry (MS). The arrows indicate the application of 20 intact oocytes, which were rapidly lysed inside the cuvette by stirring. (D) Statistical analysis of CA activity (U/ml) after subtraction of either native (4 U/ml; 20 oocytes, n = 3) or NBC-expressing oocytes (5 U/ml; 20 oocytes, n = 3), as obtained by mass spectrometry. Oocytes expressing the catalytically inactive mutant CAII-V143Y were used as control. Calibration curve of different CAI- and CAII-protein concentrations (E) to determine the amount of CA-protein expressed in oocytes (F). The asterisks above the bars for NBCe1-coexpressing oocytes (+NBCe1, 13.8 ng NBCe1-RNA) correspond to those without NBCe1-coexpression (−NBCe1). A significance level of p≤0.05 is marked with *, p≤0.01 with ** and p≤0.001 with ***.
	Figure 3. Effect of CAI or CAIII on NBCe1 transport activity.Original recordings (A) and statistics of the changes in membrane current (ΔIm; C) of NBCe1- and NBCe1+CAI- or NBCe1+CAIII-expressing oocytes during application of 5% CO2/24 mM HCO3−-buffered solution in the absence and presence of EZA (10 µM). Original recordings of ΔIm of CA-expressing control cells without coexpression of NBCe1 (B). By the use of Na+-selective microelectrodes the rates of rise of intracellular sodium concentration (ΔNa+/t; D, F) were obtained. Original recordings of ΔNa+/t of control cells without coexpression of NBCe1 (E). The asterisks above the bars correspond to the control cells without CA expression (−CA) before (−EZA) or during application of EZA (+EZA).
	Figure 4. Effect of CAI-protein injection (0–200 ng) on the catalytic activity and NBCe1 transport activity.Original recordings of the changes of intracellular proton concentration of CAI-injected oocytes (A) and of membrane current of CAI-injected, NBCe1-expressing oocytes (D) after application of 5% CO2/24 mM HCO3−-buffered solution in the absence and presence of EZA (10 µM). Rates of rise of proton concentration (B) and changes of membrane current (E) before (filled squares) or during (open squares) EZA application in CO2/HCO3−-buffered solution. EZA-sensitive rates of rise of proton concentration (C) and changes of membrane current were plotted (F). The asterisks correspond to the control cells without CA-injection (0 ng CAI).
	Figure 5. Activity and effect of CAII mutants on NBCe1 transport activity.Changes of the intracellular proton concentration as recorded in native, CAII-, CAII-H64A- and CAII-Y7F-expressing oocytes (A) to determine rates of rise of the proton concentration (B). Original recordings of the changes in membrane current (C) and intracellular sodium concentration (E) in NBCe1 and CAII-, CAII-H64A- or CAII-Y7F- coexpressing oocytes after application of 5% CO2/24 mM HCO3−-buffered solution before or during application of EZA (10 µM). Statistical analysis of membrane current (D) and rates of rise of intracellular sodium concentration (F) revealed an increase in NBCe1 transport activity after coexpression of either CAII or one of the two mutants. The asterisks above the bars correspond to the control cells without CA (−CA) before (−EZA) or during EZA (+EZA) application.
	Figure 6. Effect of injected CAII-protein on NBCe1 transport activity at different bicarbonate concentrations and constant CO2.Original recordings of membrane current (A) in NBCe1-expressing oocytes with or without injection of 50 ng CAII-protein after changing from a HEPES-buffered, bicarbonate-free saline (pH 7.0) to a 5% CO2/10 mM HCO3−-buffered saline (pH 7.0) as well as after increasing the HCO3− concentration from 10 mM (pH 7.0) to 77 mM HCO3− (pH 7.9) in a 5% CO2-equilibrated saline, before or during application of EZA (10 µM). Statistical analysis of membrane current (B) revealed an increase in NBCe1 transport activity after injection of CAII-protein in both salines. Original recordings of the change of intracellular proton concentration (C) and statistical analysis of rate of rise of proton concentration (D) of native oocytes and oocytes injected with CAII-protein. The asterisks above the bars correspond to the control cells without CA (−CA) before (−EZA) or during EZA (+EZA) application.
	Figure 7. Quantification of CAII mutants.Western blot of the different CAII mutants (CAII-Y7F, CAII-H64A and CAII-V143Y) as well as wild-type CAII (A; 12 µg total protein/lane), β-tubulin was used as loading control, and quantification of the expression of the CAII mutants in oocytes, as compared to wild-type by determination of the density of intensity (B; Density INT/mm2). Western blot of CAII-expressing and NBCe1+CAII-coexpressing oocytes, with β-tubulin used as loading control (C; 15 µg total protein/lane) and quantification of effect of NBCe1 coexpression on CAII expression rate (D).
	Figure 8. Potential binding motif (bold amino acids) of hCAII (Swiss-Prot.: P00918) against NBCe1 is incompletely conserved in N-terminus of intracellular hCAI (Swiss-Prot.: P00915) or hCAIII (Swiss-Prot.: P07451).

Alexander, Engineering the hydrophobic pocket of carbonic anhydrase II. 1991, Pubmed

Alexander, Engineering the hydrophobic pocket of carbonic anhydrase II. 1991, Pubmed
An, Chemical rescue in catalysis by human carbonic anhydrases II and III. 2002, Pubmed
Badger, Carbonic Anhydrase Activity Associated with the Cyanobacterium Synechococcus PCC7942. 1989, Pubmed
Becker, Nonenzymatic proton handling by carbonic anhydrase II during H+-lactate cotransport via monocarboxylate transporter 1. 2008, Pubmed , Xenbase
Becker, Transport activity of MCT1 expressed in Xenopus oocytes is increased by interaction with carbonic anhydrase. 2005, Pubmed , Xenbase
Becker, Carbonic anhydrase II increases the activity of the human electrogenic Na+/HCO3- cotransporter. 2007, Pubmed , Xenbase
Becker, Nonenzymatic augmentation of lactate transport via monocarboxylate transporter isoform 4 by carbonic anhydrase II. 2010, Pubmed , Xenbase
Becker, Facilitated lactate transport by MCT1 when coexpressed with the sodium bicarbonate cotransporter (NBC) in Xenopus oocytes. 2004, Pubmed , Xenbase
Becker, Intramolecular proton shuttle supports not only catalytic but also noncatalytic function of carbonic anhydrase II. 2011, Pubmed , Xenbase
Behravan, Structural and functional differences between carbonic anhydrase isoenzymes I and II as studied by site-directed mutagenesis. 1991, Pubmed
Behravan, Fine tuning of the catalytic properties of carbonic anhydrase. Studies of a Thr200----His variant of human isoenzyme II. 1990, Pubmed
Boron, Modular structure of sodium-coupled bicarbonate transporters. 2009, Pubmed
Briganti, Carbonic anhydrase activators: X-ray crystallographic and spectroscopic investigations for the interaction of isozymes I and II with histamine. 1997, Pubmed
Bröer, Characterization of the monocarboxylate transporter 1 expressed in Xenopus laevis oocytes by changes in cytosolic pH. 1998, Pubmed , Xenbase
Budayova-Spano, Production and X-ray crystallographic analysis of fully deuterated human carbonic anhydrase II. 2006, Pubmed
Deitmer, Electrogenic sodium-dependent bicarbonate secretion by glial cells of the leech central nervous system. 1991, Pubmed
Duda, Structural and kinetic analysis of the chemical rescue of the proton transfer function of carbonic anhydrase II. 2001, Pubmed
Elder, Structural and kinetic analysis of proton shuttle residues in the active site of human carbonic anhydrase III. 2007, Pubmed
Engberg, Purification and some properties of carbonic anhydrase from bovine skeletal muscle. 1985, Pubmed
Eriksson, Refined structure of bovine carbonic anhydrase III at 2.0 A resolution. 1993, Pubmed
Fierke, Functional consequences of engineering the hydrophobic pocket of carbonic anhydrase II. 1991, Pubmed
Fisher, Speeding up proton transfer in a fast enzyme: kinetic and crystallographic studies on the effect of hydrophobic amino acid substitutions in the active site of human carbonic anhydrase II. 2007, Pubmed
Fisher, Structural and kinetic characterization of active-site histidine as a proton shuttle in catalysis by human carbonic anhydrase II. 2005, Pubmed
Gramlich, Immunohistochemical localization of sodium-potassium-stimulated adenosine triphosphatase and carbonic anhydrase in human colon and colonic neoplasms. 1990, Pubmed
Gross, Regulation of the sodium bicarbonate cotransporter kNBC1 function: role of Asp(986), Asp(988) and kNBC1-carbonic anhydrase II binding. 2002, Pubmed
Jeffery, Distribution of CAIII in fetal and adult human tissue. 1980, Pubmed
Jewell, Enhancement of the catalytic properties of human carbonic anhydrase III by site-directed mutagenesis. 1991, Pubmed
Jonsson, Participation of buffer in the catalytic mechanism of carbonic anhydrase. 1976, Pubmed
Kararli, Inhibition of the hydration of CO2 catalyzed by carbonic anhydrase III from cat muscle. 1985, Pubmed
Kristensen, Expression of Na+/HCO3- co-transporter proteins (NBCs) in rat and human skeletal muscle. 2004, Pubmed
Li, Carbonic anhydrase II binds to and enhances activity of the Na+/H+ exchanger. 2002, Pubmed
LoGrasso, Catalytic enhancement of human carbonic anhydrase III by replacement of phenylalanine-198 with leucine. 1991, Pubmed
Loiselle, Regulation of the human NBC3 Na+/HCO3- cotransporter by carbonic anhydrase II and PKA. 2004, Pubmed
Lönnerholm, Amount and distribution of carbonic anhydrases CA I and CA II in the gastrointestinal tract. 1985, Pubmed
Lu, Effect of human carbonic anhydrase II on the activity of the human electrogenic Na/HCO3 cotransporter NBCe1-A in Xenopus oocytes. 2006, Pubmed , Xenbase
Luo, Physiology and pathophysiology of Na(+)/H(+) exchange isoform 1 in the central nervous system. 2007, Pubmed
Maupin, Origins of enhanced proton transport in the Y7F mutant of human carbonic anhydrase II. 2008, Pubmed
O'Dowd, Detection, characterisation, and quantification of carnosine and other histidyl derivatives in cardiac and skeletal muscle. 1988, Pubmed
Piermarini, Evidence against a direct interaction between intracellular carbonic anhydrase II and pure C-terminal domains of SLC4 bicarbonate transporters. 2007, Pubmed
Pushkin, Molecular mechanism of kNBC1-carbonic anhydrase II interaction in proximal tubule cells. 2004, Pubmed
Romero, The SLC4 family of HCO 3 - transporters. 2004, Pubmed
Scozzafava, Carbonic anhydrase activators: high affinity isozymes I, II, and IV activators, incorporating a beta-alanyl-histidine scaffold. 2002, Pubmed
Silverman, Carbonic anhydrase: oxygen-18 exchange catalyzed by an enzyme with rate-contributing proton-transfer steps. 1982, Pubmed
Sly, Human carbonic anhydrases and carbonic anhydrase deficiencies. 1995, Pubmed
Sterling, Carbonic anhydrase: in the driver's seat for bicarbonate transport. 2001, Pubmed
Sültemeyer, Mass Spectrometric Measurement of Intracellular Carbonic Anhydrase Activity in High and Low C(i) Cells of Chlamydomonas: Studies Using O Exchange with C/O Labeled Bicarbonate. 1990, Pubmed
Swietach, Spatial regulation of intracellular pH in multicellular strands of neonatal rat cardiomyocytes. 2010, Pubmed
Tashian, The carbonic anhydrases: widening perspectives on their evolution, expression and function. 1989, Pubmed
Tu, Buffer enhancement of proton transfer in catalysis by human carbonic anhydrase III. 1990, Pubmed
Tu, Role of histidine 64 in the catalytic mechanism of human carbonic anhydrase II studied with a site-specific mutant. 1989, Pubmed
Vaughan-Jones, Intrinsic H(+) ion mobility in the rabbit ventricular myocyte. 2002, Pubmed
Vince, Identification of the carbonic anhydrase II binding site in the Cl(-)/HCO(3)(-) anion exchanger AE1. 2000, Pubmed
Vince, Carbonic anhydrase II binds to the carboxyl terminus of human band 3, the erythrocyte C1-/HCO3- exchanger. 1998, Pubmed
Vince, Localization of the Cl-/HCO3- anion exchanger binding site to the amino-terminal region of carbonic anhydrase II. 2000, Pubmed
Weise, Enzymatic suppression of the membrane conductance associated with the glutamine transporter SNAT3 expressed in Xenopus oocytes by carbonic anhydrase II. 2007, Pubmed , Xenbase
Weise, Substrate-dependent interference of carbonic anhydrases with the glutamine transporter SNAT3-induced conductance. 2011, Pubmed , Xenbase
Wendel, The sodium-bicarbonate cotransporter NBCe1 supports glutamine efflux via SNAT3 (SLC38A3) co-expressed in Xenopus oocytes. 2008, Pubmed , Xenbase
Yamada, Functional role of a putative carbonic anhydrase II-binding domain in the electrogenic Na+ -HCO₃- cotransporter NBCe1 expressed in Xenopus oocytes. 2011, Pubmed , Xenbase
Yu, Secretagogue stimulation enhances NBCe1 (electrogenic Na(+)/HCO(3)(-) cotransporter) surface expression in murine colonic crypts. 2009, Pubmed