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The sodium-dicarboxylate cotransporters (SLC 13), which transport succinate and other Krebs cycle intermediates, fall into 2 categories based on their substrate affinity, low affinity and high affinity. Both the low- and high-affinity transporters play an important role in the handling of citrate by the kidneys. The two different Na+-coupled dicarboxylate transporters (NADC) have been identified in mammalian tissues. These are NADC1 and NADC3 (NADC2 is found in C. Elegans). NADC1 is Na+-coupled, electrogenic, and exhibits low affinity for its dicarboxylate substrates. This isoform is expressed primarily in the brush border membrane of intestinal and renal epithelial cells. The physiological function of NADC1 is to absorb the intermediates of the citric acid cycle, such as citrate, succinate, alpha-ketoglutarate, fumarate, and malate, in the intestine and kidney. NADC3 is also a Na+-coupled and electrogenic dicarboxylate transporter, but it exhibits relatively higher affinity for its substrates compared with NADC1. The NADC3 is expressed primarily in the basolateral membrane of intestinal and renal epithelial cells. However, it is also found in tissues such as liver, placenta, and brain. NADC3 in the kidney is involved in generating the driving force for the organic anion transporter OAT1 to facilitate the active entry of organic anions into the tubular cells across the basolateral membrane. In the brain, NADC3 mediates the cellular uptake of N-acetylaspartate, a process closely linked to myelination. Therefore, the physiological functions of the NADC may extend beyond the mediation of cellular entry of citric acid cycle intermediates. Recently, a third member of this family in mammals has been identified, Na+-coupled citrate transporter (NACT), mediates the cellular uptake of citrate in a Na+-coupled manner.

NADC-1, (SLC13A2 gene) is involved in a sodium dicarboxylate cotransport, an electrogenic process, coupling 3 sodium ions to the transport of each divalent anion substrate. NADC-1 is a 586aa protein in mouse, 587aa in rat and 592aa in human (chr 17p11.1-q11.1). Invitro translation of human NADC-1 produced an approximately 48kD protein. The deduced aa sequence of human NADC-1 is 78% identical to rabbit NADC-1 and 47% to rat sodium sulfate transporter. NADC-1 transporter is a low affinity, sodium dependent, and pH-insensitive transporter of succinate, its transport of citrate is stimulated by acidic pH.

NADC-3, (SCL13A3 gene) a sodium dependent high- affinity dicarboxylate transporter with 600aa each in mouse and rat, it's a 602aa sequence in human (chr 20q12-q13.1) expressed in kidney, brain, liver and placenta. NADC-3 exhibits 48% identity with NADC-1. The transport function of NADC-3 shows a sigmoidal relationship with regard to Na+ concentration, NADC3 accepts a number of dicarboxylates including dimethyl-succinate as substrates and excludes monocarboxylates. Transport of succinate is markedly influenced by pH; the transport gradually decreases when pH is acidic.

NACT, is 568aa protein in human (chr 17p13.2) and 572aa in rat, NaCT is expressed in liver, testis and brain in rat and shows preference for citrate over dicarboxylates; it may play a role in cellular utilization of citrate in blood for the synthesis of fatty acids and cholesterol and for the generation of energy.

m=mouse; r=rat; h=human; b=bovine; c=chicken; d=dog; ~CT or ~NT=near C or N-terminus. EC=Extracellular; CL=Cytoplasmic loop;

* Expected antibody crossreactivity information is mostly based upon high (>70%) sequence conservation of antigenic/control peptides in various species. When antibody crossreactivity has actually been experimentally confirmed in various species, it will be mentioned in the appropriate data sheets.

"Neat Antisera or antisera" are the unpurified antiserum and it is suitable for ELISA and Western.
"Affinity pure" IgG may be more suitable for immunohistochemical (IHC) applications and to reduce background in most immunological applications including ELISA and Western.
"Control peptides" can not be used for Western as they are very short peptides. They are intended for ELISA or antibody blocking studies to establish antibody specificity.
Western blot +ve protein controls, where available, are semi-pure, pure or recombinant proteins that are formulated in SDS-PAGE sample buffer. They are recommended to be used for Western (load 10 ul/lane) for visualization with antibodies

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