PMID:20568736

2010-10-27T15:30:26Z

Klaus.fendler:

{{RightTOC}}
<protect>
 '''Garcia-Celma, JJ, Ploch, J, Smirnova, I, Kaback, HR and Fendler, K''' (2010) Delineating electrogenic reactions during lactose/H+ symport.''Biochemistry'' '''49''':6115-21

{|{{Prettytable}} align = 'center' width= '70%'
|-
|{{TableHeadingColor}} |'''Abstract''' || <protect>Electrogenic reactions accompanying downhill lactose/H(+) symport catalyzed by the lactose permease of Escherichia coli (LacY) have been assessed using solid-supported membrane-based electrophysiology with improved time resolution. Rates of charge translocation generated by purified LacY reconstituted into proteoliposomes were analyzed over a pH range from 5.2 to 8.5, which allows characterization of two electrogenic steps in the transport mechanism: (i) a weak electrogenic reaction triggered by sugar binding and observed under conditions where H(+) translocation is abolished either by acidic pH or by a Glu325 --> Ala mutation in the H(+) binding site (this step with a rate constant of approximately 200 s(-1) for wild-type LacY leads to an intermediate proposed to represent an "occluded" state) and (ii) a major electrogenic reaction corresponding to 94% of the total charge translocated at pH 8, which is pH-dependent with a maximum rate of approximately 30 s(-1) and a pK of 7.5. This partial reaction is assigned to rate-limiting H(+) release on the cytoplasmic side of LacY during turnover. These findings together with previous electrophysiological results and biochemical-biophysical studies are included in an overall kinetic mechanism that allows delineation of the electrogenic steps in the reaction pathway.</protect>
|-
|{{TableHeadingColor}} nowrap |'''Links''' ||
* [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=20568736 PubMed]
Online version:[http://dx.doi.org/10.1021/bi100492p 10.1021/bi100492p]
|}
</protect>
==Significance {{HelpIcon|Help:Literature}} ==
First assignment of electrogenic steps (partial reactions that displace electric charge) in the LacY reaction cycle.

== Useful Materials and Methods {{HelpIcon|Help:Literature}}==
This study uses an unconventional electrophysiological technique based on solid supported membranes.
For details see [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WN5-4T3TKHR-1&_user=43608&_coverDate=10%2F31%2F2008&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000004571&_version=1&_urlVersion=0&_userid=43608&md5=62088029d5774f30549d4b3d3b688bce&searchtype=a]

==Annotations {{HelpIcon|Help:Literature}}==
<protect>

{| id="N4c99b10bf0696" class=" tableEdit GO_table_reference"
|- {{table heading style}}
!|Gene product!!Qualifier!!GO ID!!GO term name!!Evidence Code!!with/from!!Aspect!!Notes!!Status

|- class="tableEdit_footer"
|[{{SERVER}}{{SCRIPTPATH}}?title=Special:TableEdit&id=63ce1649aab8b3180235b0af7618f667.176174.N4c99b10bf0696&page=176174&pagename={{FULLPAGENAMEE}}&type=0&template=GO_table_reference edit table] || || || || || || || ||
|}
</protect>

==EcoliWiki Links {{HelpIcon|Help:Literature}} ==
{{LitLinks}}

==See also==
[http://www.pnas.org/content/106/18/7373.long]
==References==
{{RefHelp}}
<references/>

PMID:20568736

2010-10-27T15:20:37Z

Klaus.fendler:

{{RightTOC}}
<protect>
 '''Garcia-Celma, JJ, Ploch, J, Smirnova, I, Kaback, HR and Fendler, K''' (2010) Delineating electrogenic reactions during lactose/H+ symport.''Biochemistry'' '''49''':6115-21

{|{{Prettytable}} align = 'center' width= '70%'
|-
|{{TableHeadingColor}} |'''Abstract''' || <protect>Electrogenic reactions accompanying downhill lactose/H(+) symport catalyzed by the lactose permease of Escherichia coli (LacY) have been assessed using solid-supported membrane-based electrophysiology with improved time resolution. Rates of charge translocation generated by purified LacY reconstituted into proteoliposomes were analyzed over a pH range from 5.2 to 8.5, which allows characterization of two electrogenic steps in the transport mechanism: (i) a weak electrogenic reaction triggered by sugar binding and observed under conditions where H(+) translocation is abolished either by acidic pH or by a Glu325 --> Ala mutation in the H(+) binding site (this step with a rate constant of approximately 200 s(-1) for wild-type LacY leads to an intermediate proposed to represent an "occluded" state) and (ii) a major electrogenic reaction corresponding to 94% of the total charge translocated at pH 8, which is pH-dependent with a maximum rate of approximately 30 s(-1) and a pK of 7.5. This partial reaction is assigned to rate-limiting H(+) release on the cytoplasmic side of LacY during turnover. These findings together with previous electrophysiological results and biochemical-biophysical studies are included in an overall kinetic mechanism that allows delineation of the electrogenic steps in the reaction pathway.</protect>
|-
|{{TableHeadingColor}} nowrap |'''Links''' ||
* [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=20568736 PubMed]
Online version:[http://dx.doi.org/10.1021/bi100492p 10.1021/bi100492p]
|}
</protect>
==Significance {{HelpIcon|Help:Literature}} ==
{{LitSignificance}}

== Useful Materials and Methods {{HelpIcon|Help:Literature}}==
{{LitMaterials}}

==Annotations {{HelpIcon|Help:Literature}}==
<protect>

{| id="N4c99b10bf0696" class=" tableEdit GO_table_reference"
|- {{table heading style}}
!|Gene product!!Qualifier!!GO ID!!GO term name!!Evidence Code!!with/from!!Aspect!!Notes!!Status

|- class="tableEdit_footer"
|[{{SERVER}}{{SCRIPTPATH}}?title=Special:TableEdit&id=63ce1649aab8b3180235b0af7618f667.176174.N4c99b10bf0696&page=176174&pagename={{FULLPAGENAMEE}}&type=0&template=GO_table_reference edit table] || || || || || || || ||
|}
</protect>

==EcoliWiki Links {{HelpIcon|Help:Literature}} ==
{{LitLinks}}

==See also==
[http://www.pnas.org/content/106/18/7373.long]
==References==
{{RefHelp}}
<references/>

EcoliWiki - User contributions [en]

PMID:20568736

PMID:20568736