Physiology Article Figure Interpretation- Please Help! please help me with under
ID: 68522 • Letter: P
Question
Physiology Article Figure Interpretation- Please Help!
please help me with understanding each part of the figure. the methods used, any controls, and the main point of figures.
Urate exists primarily as a weak acid at physiological pH with a pKa value of 5.75 (ref. 10); therefore, the structure of the urate transporter should be similar to that of members of the organic anion transporter (OAT) family10,12–14. We systematically identified paralogues of OATs in the entire draft human genome database15, and identified a sequence that seemed to be similar to the OAT4 gene14 in chromosome 11q13. We predicted the structure of this gene (SLC22A12), and succeeded in isolating the complementary DNA (URAT1, 2,642 base pairs, bp) from human kidney poly(A)þ RNA by 30 rapid amplification of cDNA ends (30-RACE). The amino-acid sequence predicted by the URAT1 cDNA exhibits 42% amino-acid identity with that of OAT4 (ref. 14) (Fig. 1a). The hydropathy plot predicted 12 membrane-spanning domains in URAT1, which are similar to those in members of OAT family12–14. Northern blotting of human tissues revealed substantial hybrid- ization with a 2.8-kilobase (kb) transcript in human adult and fetal kidney (Fig. 1b).
Explanation / Answer
From the given data,
The salts and ions of uric acid is called urate, which is an organic compound excreted via urine in almost all ureotelic animals. If this compound is not filtered or excreted from the blood, it results occurrence of a disease called gout. In this condition urate crystals accumulate at joints and causes rheumatic pain. Therefore, the urate transporter (an organic anion transporter) transports urate in the kidney cells (nephrons).
The urate transports is paralogous to the organic anion transporter and the urate transporter gene is a duplicate gene of organic anion transporter (OTA), therefore these two genes have homology. In the experiment, they isolated the cDNA of urate transporter and compared it with OTA gene, which shows 42% of shared similarity or homology.
The hydropathy plot index (presence of same hydrophobic amino acids at the same position) is also similar between urate transporter and OTA gene. The report Northern blot shows that the fatal kidney express more urate transporters than adults kidney cells and the OTA gene is used as marker for identification of urate transporter in northern blot.
The histochemical analysis (tissue studies) shown that the urate transporter s are specifically located in luminal membrane of the epithelium of proximal tubules, but not in that of distal tubules. From northern blot analysis the molecular weight of urate transporters is recognized, which is about 40,000 Daltons. An antigen peptide seems to have inhibitory action against urate transporter.
The urate transporter has following features: