Modulation of renal type IIa Na+/Pi cotransporter kinetics by the arginine modifier phenylglyoxal.
The effects of the arginine-modifying reagent phenylglyoxal on the kinetics of the type IIa Na + /Pi cotransporter expressed in Xenopus, oocytes were studied by means of 32Pi uptake and electrophysiology. Phenylglyoxal incubation induced up to 60% loss of cotransport function but only marginally altered the Na+-leak. Substrate activation and pH dependency remained essentially unaltered, whereas the voltage dependency of Pi-induced change in electrogenic response was significantly reduced. Presteady-state charge movements were suppressed and the equilibrium charge distribution was shifted slightly towards hyperpolarizing potentials. Charge movements in the absence of external Na+ were also suppressed, which indicated that the empty-carrier kinetics were modified. These effects were incorporated into an ordered alternating access model for NaPi-IIa, whereby the arginine modification by phenylglyoxal was modeled as altered apparent electrical distances moved by mobile charges, together with a slower rate of translocation of the electroneutral, fully loaded carrier.
Forster
I C
IC
Physiologisches Institut, Universität Zürich-Irchel, Winterthurerstr. 190, CH-8057, Switzerland. iforster@access.unizh.ch
Köhler
K
K
Stange
G
G
Biber
J
J
Murer
H
H
D000818:Animals; D001120:Arginine / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D003198:Computer Simulation; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000502:physiology; D015640:Ion Channel Gating / Q000235:genetics / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects* / Q000502:physiology; D008954:Models, Biological; D009865:Oocytes / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D010658:Phenylglyoxal / Q000494:pharmacology*; D010758:Phosphorus / Q000378:metabolism; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters / Q000235:genetics* / Q000378:metabolism*; D014982:Xenopus laevis
D004791:Enzyme Inhibitors; D050608:Sodium-Phosphate Cotransporter Proteins; D027981:Symporters; D010758:Phosphorus; D001120:Arginine; D010658:Phenylglyoxal