{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,18]],"date-time":"2025-10-18T20:29:31Z","timestamp":1760819371422},"reference-count":18,"publisher":"Wiley","issue":"8","license":[{"start":{"date-parts":[[2008,12,31]],"date-time":"2008-12-31T00:00:00Z","timestamp":1230681600000},"content-version":"vor","delay-in-days":2709,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Protein Science"],"published-print":{"date-parts":[[2001,8]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>The water channel protein aquaporin\u20101 (AQP1) has two asparagine\u2010proline\u2010alanine (NPA) repeats on loops B and E. From recent structural information, these loops are on opposite sides of the membrane and meet to form a pore. We replaced the mercury\u2010sensitive residue cysteine 189 in AQP1 by serine to obtain a mercury\u2010insensitive template (C189S). Subsequently, we substituted three consecutive cysteines for residues 71\u201373 near the first NPA repeat (76\u201378) in intracellular loop B, and investigated whether they were accessible to extracellular mercurials. AQP1 and its mutants were expressed in <jats:italic>Xenopus laevis<\/jats:italic> oocytes, and the osmotic permeability (P<jats:sub>f<\/jats:sub>) of the oocytes was determined. C189S had wild\u2010type P<jats:sub>f<\/jats:sub> but was not sensitive to HgCl<jats:sub>2<\/jats:sub>. Expression of all three C189S cysteine mutants resulted in increased P<jats:sub>f<\/jats:sub>, and all three mutants regained mercurial sensitivity. These results, especially the inhibitions by the large mercurial p\u2010chloromercunbenzene\u2010sulfonic acid (pCMBS) (\u223c6\u00c5 wide), suggest that residues 71\u201373 at the pore are accessible to extracellular mercurials. A 30\u2010ps molecular dynamics simulation (at 300 K) starting with crystallographic coordinates of AQP1 showed that the width of the pore bottleneck (between Connolly surfaces) can vary (w<jats:sub>avg<\/jats:sub> = 3.9 \u00c5, \u03c3 = 0.75; hydrated AQP1). Thus, although the pore width would be \u2265 6 \u00c5 only for 0.0026 of the time, this might suffice for pCMBS to reach residues 71\u201373. Alternative explanations such as passage of pCMBS across the AQP1 tetramer center or other unspecified transmembrane pathways cannot be excluded.<\/jats:p>","DOI":"10.1110\/ps.5901","type":"journal-article","created":{"date-parts":[[2002,7,26]],"date-time":"2002-07-26T23:59:58Z","timestamp":1027727998000},"page":"1627-1634","source":"Crossref","is-referenced-by-count":9,"title":["Mercurial sensitivity of aquaporin 1 endofacial loop B residues"],"prefix":"10.1002","volume":"10","author":[{"given":"Kunyan","family":"Kuang","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jorge F.","family":"Haller","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Guangpu","family":"Shi","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Fengying","family":"Kang","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Min","family":"Cheung","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Pavel","family":"Iserovich","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jorge","family":"Fischbarg","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2008,12,31]]},"reference":[{"key":"e_1_2_7_2_1","doi-asserted-by":"publisher","DOI":"10.1126\/science.1384130"},{"key":"e_1_2_7_3_1","doi-asserted-by":"publisher","DOI":"10.1038\/42517"},{"key":"e_1_2_7_4_1","doi-asserted-by":"publisher","DOI":"10.1016\/B978-0-12-550640-3.50032-0"},{"key":"e_1_2_7_5_1","doi-asserted-by":"publisher","DOI":"10.1126\/science.6879170"},{"key":"e_1_2_7_6_1","doi-asserted-by":"publisher","DOI":"10.1152\/ajpcell.1993.265.5.C1349"},{"key":"e_1_2_7_7_1","doi-asserted-by":"publisher","DOI":"10.1126\/science.290.5491.481"},{"key":"e_1_2_7_8_1","doi-asserted-by":"publisher","DOI":"10.1006\/jmbi.1999.3413"},{"key":"e_1_2_7_9_1","doi-asserted-by":"publisher","DOI":"10.1016\/S0021-9258(17)36674-7"},{"key":"e_1_2_7_10_1","doi-asserted-by":"publisher","DOI":"10.1006\/jsbi.1999.4177"},{"key":"e_1_2_7_11_1","doi-asserted-by":"publisher","DOI":"10.1038\/35036519"},{"key":"e_1_2_7_12_1","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.88.24.11110"},{"key":"e_1_2_7_13_1","doi-asserted-by":"publisher","DOI":"10.1016\/S0021-9258(18)54108-9"},{"key":"e_1_2_7_14_1","doi-asserted-by":"publisher","DOI":"10.1006\/jmbi.2000.3949"},{"key":"e_1_2_7_15_1","doi-asserted-by":"publisher","DOI":"10.1073\/pnas.98.4.1398"},{"key":"e_1_2_7_16_1","doi-asserted-by":"publisher","DOI":"10.1021\/bi0004403"},{"key":"e_1_2_7_17_1","doi-asserted-by":"crossref","first-page":"21505","DOI":"10.1016\/S0021-9258(20)80569-9","article-title":"Amino acids lining the channel of the gamma\u2010aminobutyric acid type A receptor identified by cysteine substitution","volume":"268","author":"Xu M.","year":"1993","journal-title":"J. Biol. 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