The effect of pH on interaction of nitrobenzylthioinosine and hydroxynitrobenzylthioinosine with the nucleoside transporter of human erythrocyte membranes
Site-specific binding to human erythrocyte membranes of nitrobenzylthioinosine (NBMPR), un-ionized at physiological pH, was compared with that of hydroxynitrobenzylthioinosine (HNBMPR), pKa 6.4, at graded pH values. Binding of [3H]NBMPR was measured directly, and that of HNBMPR was assayed by compet...
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| Veröffentlicht in: | Molecular pharmacology 1985-06, Vol.27 (6), p.662-665 |
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| creator | Cass, C E Gati, W P Odegard, R Paterson, A R |
| description | Site-specific binding to human erythrocyte membranes of nitrobenzylthioinosine (NBMPR), un-ionized at physiological pH, was
compared with that of hydroxynitrobenzylthioinosine (HNBMPR), pKa 6.4, at graded pH values. Binding of [3H]NBMPR was measured
directly, and that of HNBMPR was assayed by competitive inhibition by HNBMPR of [3H]NBMPR binding. Kd and Bmax values for
binding of [3H]NBMPR to erythrocyte membranes were independent of pH. Kd values for the competing ligand were determined by
mass law analysis of equilibrium binding data using either (a) apparent ligand concentration (dissociated plus undissociated
forms of HNBMPR) or (b) the concentration of undissociated HNBMPR. Kd values for HNBMPR calculated with the apparent ligand
concentration increased 10-fold as the fraction of HNBMPR molecules present in the dissociated form was increased (by pH changes)
from 14 to 88%, whereas Kd values for the undissociated form of HNBMPR were independent of pH. The results presented here
demonstrate that the undissociated form of HNBMPR binds more tightly to the transport-inhibitory sites of erythrocytes than
NBMPR and suggest that ionization of S6-substituted thiopurine ribonucleosides eliminates or greatly decreases their ability
to interact with the binding sites. |
| format | Article |
| fullrecord | <record><control><sourceid>proquest_pubme</sourceid><recordid>TN_cdi_proquest_miscellaneous_76126527</recordid><sourceformat>XML</sourceformat><sourcesystem>PC</sourcesystem><sourcerecordid>76126527</sourcerecordid><originalsourceid>FETCH-LOGICAL-h236t-fe82d5e84949df07c2d398f4f37f2e0e94376abc13ccbc2f7fc7fe0a0cc4d46c3</originalsourceid><addsrcrecordid>eNp1kEFLxDAQhYso67r6E4Rc9FZI0jZtj7KoKyx4WcFbSdPJJtImNUlZ60_x1xrZvXqax7yP94Y5S5akoCTFhJDzZIkxZWlVF--XyZX3HxiTvKjwIlnkOGpcL5OfnQIEUoIIyEo0bpA1SJsAjougo45Lo4OzLZjvuQ9KW22s1wYQNx1Sc-fs1_wPcdBBoRALzCR6iLsOUHDc-NG62PCXraaBGwRuDspZMQdAAwxtZMBfJxeS9x5uTnOVvD097tabdPv6_LJ-2KaKZiykEiraFVDldV53EpeCdlldyVxmpaSAoc6zkvFWkEyIVlBZSlFKwBwLkXc5E9kquT_mjs5-TuBDM2gvoO_jEXbyTckIZQUtI3h7Aqd2gK4ZnR64m5vTM6N_d_SV3quDdtCMiruBC9vb_dzQsmENYzT7BWs3hXA</addsrcrecordid><sourcetype>Aggregation Database</sourcetype><iscdi>true</iscdi><recordtype>article</recordtype><pqid>76126527</pqid></control><display><type>article</type><title>The effect of pH on interaction of nitrobenzylthioinosine and hydroxynitrobenzylthioinosine with the nucleoside transporter of human erythrocyte membranes</title><source>MEDLINE</source><source>EZB-FREE-00999 freely available EZB journals</source><creator>Cass, C E ; Gati, W P ; Odegard, R ; Paterson, A R</creator><creatorcontrib>Cass, C E ; Gati, W P ; Odegard, R ; Paterson, A R</creatorcontrib><description>Site-specific binding to human erythrocyte membranes of nitrobenzylthioinosine (NBMPR), un-ionized at physiological pH, was
compared with that of hydroxynitrobenzylthioinosine (HNBMPR), pKa 6.4, at graded pH values. Binding of [3H]NBMPR was measured
directly, and that of HNBMPR was assayed by competitive inhibition by HNBMPR of [3H]NBMPR binding. Kd and Bmax values for
binding of [3H]NBMPR to erythrocyte membranes were independent of pH. Kd values for the competing ligand were determined by
mass law analysis of equilibrium binding data using either (a) apparent ligand concentration (dissociated plus undissociated
forms of HNBMPR) or (b) the concentration of undissociated HNBMPR. Kd values for HNBMPR calculated with the apparent ligand
concentration increased 10-fold as the fraction of HNBMPR molecules present in the dissociated form was increased (by pH changes)
from 14 to 88%, whereas Kd values for the undissociated form of HNBMPR were independent of pH. The results presented here
demonstrate that the undissociated form of HNBMPR binds more tightly to the transport-inhibitory sites of erythrocytes than
NBMPR and suggest that ionization of S6-substituted thiopurine ribonucleosides eliminates or greatly decreases their ability
to interact with the binding sites.</description><identifier>ISSN: 0026-895X</identifier><identifier>EISSN: 1521-0111</identifier><identifier>PMID: 4000109</identifier><language>eng</language><publisher>United States: American Society for Pharmacology and Experimental Therapeutics</publisher><subject>Affinity Labels - pharmacology ; Binding, Competitive ; Blood Proteins - metabolism ; Carrier Proteins - metabolism ; Erythrocyte Membrane - drug effects ; Erythrocyte Membrane - metabolism ; Guanosine - analogs & derivatives ; Guanosine - pharmacology ; Humans ; Hydrogen-Ion Concentration ; Inosine - analogs & derivatives ; Kinetics ; Membrane Proteins - metabolism ; Nucleoside Transport Proteins ; Thioinosine - analogs & derivatives ; Thioinosine - pharmacology ; Thionucleosides - pharmacology</subject><ispartof>Molecular pharmacology, 1985-06, Vol.27 (6), p.662-665</ispartof><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>314,780,784</link.rule.ids><backlink>$$Uhttps://www.ncbi.nlm.nih.gov/pubmed/4000109$$D View this record in MEDLINE/PubMed$$Hfree_for_read</backlink></links><search><creatorcontrib>Cass, C E</creatorcontrib><creatorcontrib>Gati, W P</creatorcontrib><creatorcontrib>Odegard, R</creatorcontrib><creatorcontrib>Paterson, A R</creatorcontrib><title>The effect of pH on interaction of nitrobenzylthioinosine and hydroxynitrobenzylthioinosine with the nucleoside transporter of human erythrocyte membranes</title><title>Molecular pharmacology</title><addtitle>Mol Pharmacol</addtitle><description>Site-specific binding to human erythrocyte membranes of nitrobenzylthioinosine (NBMPR), un-ionized at physiological pH, was
compared with that of hydroxynitrobenzylthioinosine (HNBMPR), pKa 6.4, at graded pH values. Binding of [3H]NBMPR was measured
directly, and that of HNBMPR was assayed by competitive inhibition by HNBMPR of [3H]NBMPR binding. Kd and Bmax values for
binding of [3H]NBMPR to erythrocyte membranes were independent of pH. Kd values for the competing ligand were determined by
mass law analysis of equilibrium binding data using either (a) apparent ligand concentration (dissociated plus undissociated
forms of HNBMPR) or (b) the concentration of undissociated HNBMPR. Kd values for HNBMPR calculated with the apparent ligand
concentration increased 10-fold as the fraction of HNBMPR molecules present in the dissociated form was increased (by pH changes)
from 14 to 88%, whereas Kd values for the undissociated form of HNBMPR were independent of pH. The results presented here
demonstrate that the undissociated form of HNBMPR binds more tightly to the transport-inhibitory sites of erythrocytes than
NBMPR and suggest that ionization of S6-substituted thiopurine ribonucleosides eliminates or greatly decreases their ability
to interact with the binding sites.</description><subject>Affinity Labels - pharmacology</subject><subject>Binding, Competitive</subject><subject>Blood Proteins - metabolism</subject><subject>Carrier Proteins - metabolism</subject><subject>Erythrocyte Membrane - drug effects</subject><subject>Erythrocyte Membrane - metabolism</subject><subject>Guanosine - analogs & derivatives</subject><subject>Guanosine - pharmacology</subject><subject>Humans</subject><subject>Hydrogen-Ion Concentration</subject><subject>Inosine - analogs & derivatives</subject><subject>Kinetics</subject><subject>Membrane Proteins - metabolism</subject><subject>Nucleoside Transport Proteins</subject><subject>Thioinosine - analogs & derivatives</subject><subject>Thioinosine - pharmacology</subject><subject>Thionucleosides - pharmacology</subject><issn>0026-895X</issn><issn>1521-0111</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>1985</creationdate><recordtype>article</recordtype><sourceid>EIF</sourceid><recordid>eNp1kEFLxDAQhYso67r6E4Rc9FZI0jZtj7KoKyx4WcFbSdPJJtImNUlZ60_x1xrZvXqax7yP94Y5S5akoCTFhJDzZIkxZWlVF--XyZX3HxiTvKjwIlnkOGpcL5OfnQIEUoIIyEo0bpA1SJsAjougo45Lo4OzLZjvuQ9KW22s1wYQNx1Sc-fs1_wPcdBBoRALzCR6iLsOUHDc-NG62PCXraaBGwRuDspZMQdAAwxtZMBfJxeS9x5uTnOVvD097tabdPv6_LJ-2KaKZiykEiraFVDldV53EpeCdlldyVxmpaSAoc6zkvFWkEyIVlBZSlFKwBwLkXc5E9kquT_mjs5-TuBDM2gvoO_jEXbyTckIZQUtI3h7Aqd2gK4ZnR64m5vTM6N_d_SV3quDdtCMiruBC9vb_dzQsmENYzT7BWs3hXA</recordid><startdate>198506</startdate><enddate>198506</enddate><creator>Cass, C E</creator><creator>Gati, W P</creator><creator>Odegard, R</creator><creator>Paterson, A R</creator><general>American Society for Pharmacology and Experimental Therapeutics</general><scope>CGR</scope><scope>CUY</scope><scope>CVF</scope><scope>ECM</scope><scope>EIF</scope><scope>NPM</scope><scope>7X8</scope></search><sort><creationdate>198506</creationdate><title>The effect of pH on interaction of nitrobenzylthioinosine and hydroxynitrobenzylthioinosine with the nucleoside transporter of human erythrocyte membranes</title><author>Cass, C E ; Gati, W P ; Odegard, R ; Paterson, A R</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-h236t-fe82d5e84949df07c2d398f4f37f2e0e94376abc13ccbc2f7fc7fe0a0cc4d46c3</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>1985</creationdate><topic>Affinity Labels - pharmacology</topic><topic>Binding, Competitive</topic><topic>Blood Proteins - metabolism</topic><topic>Carrier Proteins - metabolism</topic><topic>Erythrocyte Membrane - drug effects</topic><topic>Erythrocyte Membrane - metabolism</topic><topic>Guanosine - analogs & derivatives</topic><topic>Guanosine - pharmacology</topic><topic>Humans</topic><topic>Hydrogen-Ion Concentration</topic><topic>Inosine - analogs & derivatives</topic><topic>Kinetics</topic><topic>Membrane Proteins - metabolism</topic><topic>Nucleoside Transport Proteins</topic><topic>Thioinosine - analogs & derivatives</topic><topic>Thioinosine - pharmacology</topic><topic>Thionucleosides - pharmacology</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Cass, C E</creatorcontrib><creatorcontrib>Gati, W P</creatorcontrib><creatorcontrib>Odegard, R</creatorcontrib><creatorcontrib>Paterson, A R</creatorcontrib><collection>Medline</collection><collection>MEDLINE</collection><collection>MEDLINE (Ovid)</collection><collection>MEDLINE</collection><collection>MEDLINE</collection><collection>PubMed</collection><collection>MEDLINE - Academic</collection><jtitle>Molecular pharmacology</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Cass, C E</au><au>Gati, W P</au><au>Odegard, R</au><au>Paterson, A R</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>The effect of pH on interaction of nitrobenzylthioinosine and hydroxynitrobenzylthioinosine with the nucleoside transporter of human erythrocyte membranes</atitle><jtitle>Molecular pharmacology</jtitle><addtitle>Mol Pharmacol</addtitle><date>1985-06</date><risdate>1985</risdate><volume>27</volume><issue>6</issue><spage>662</spage><epage>665</epage><pages>662-665</pages><issn>0026-895X</issn><eissn>1521-0111</eissn><abstract>Site-specific binding to human erythrocyte membranes of nitrobenzylthioinosine (NBMPR), un-ionized at physiological pH, was
compared with that of hydroxynitrobenzylthioinosine (HNBMPR), pKa 6.4, at graded pH values. Binding of [3H]NBMPR was measured
directly, and that of HNBMPR was assayed by competitive inhibition by HNBMPR of [3H]NBMPR binding. Kd and Bmax values for
binding of [3H]NBMPR to erythrocyte membranes were independent of pH. Kd values for the competing ligand were determined by
mass law analysis of equilibrium binding data using either (a) apparent ligand concentration (dissociated plus undissociated
forms of HNBMPR) or (b) the concentration of undissociated HNBMPR. Kd values for HNBMPR calculated with the apparent ligand
concentration increased 10-fold as the fraction of HNBMPR molecules present in the dissociated form was increased (by pH changes)
from 14 to 88%, whereas Kd values for the undissociated form of HNBMPR were independent of pH. The results presented here
demonstrate that the undissociated form of HNBMPR binds more tightly to the transport-inhibitory sites of erythrocytes than
NBMPR and suggest that ionization of S6-substituted thiopurine ribonucleosides eliminates or greatly decreases their ability
to interact with the binding sites.</abstract><cop>United States</cop><pub>American Society for Pharmacology and Experimental Therapeutics</pub><pmid>4000109</pmid><tpages>4</tpages></addata></record> |
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| identifier | ISSN: 0026-895X |
| ispartof | Molecular pharmacology, 1985-06, Vol.27 (6), p.662-665 |
| issn | 0026-895X 1521-0111 |
| language | eng |
| recordid | cdi_proquest_miscellaneous_76126527 |
| source | MEDLINE; EZB-FREE-00999 freely available EZB journals |
| subjects | Affinity Labels - pharmacology Binding, Competitive Blood Proteins - metabolism Carrier Proteins - metabolism Erythrocyte Membrane - drug effects Erythrocyte Membrane - metabolism Guanosine - analogs & derivatives Guanosine - pharmacology Humans Hydrogen-Ion Concentration Inosine - analogs & derivatives Kinetics Membrane Proteins - metabolism Nucleoside Transport Proteins Thioinosine - analogs & derivatives Thioinosine - pharmacology Thionucleosides - pharmacology |
| title | The effect of pH on interaction of nitrobenzylthioinosine and hydroxynitrobenzylthioinosine with the nucleoside transporter of human erythrocyte membranes |
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