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P-C4-20 Role of acidic phospholipids in subsequent steps of preprotein translocation in E. coli
P-c4-17
GRAMlClDli CHANNELFUNCTION ANDL&PlDCURVATURE MAER AM.. LUNDBAEK JA., PROVIDENCE LL., ANDERSENOS. Dept. of F’hysidogy ad Biophysics. Medic+ College, New York, USA
Cornell
University
Purpose: We tested the relatio11betweeu the lipid molecular shapeat1d the 1nembraue defonnatiou energy. The bg-amicidincbaunel ftuiction varies wit11the spontaneouscurvature of the bilayer, which can be altered by changes in [I-I+], [Ca”] and ionic strengtlth. Methods: Single channelexperilnents were doue using the bilayer puucl1(Audersen, 1983). Results: DecreasiugpH fro1118 to 3 has 110 effect on conductance(8) but reducestl1e averageduratio11(T) and the channel fonni11g potency. Iucreasing[Na’] from 0. I M to I M has no effect on g but decreases‘I. Increasi11g [Ca”] from 3nM to ImM decreasesg and T. Conclusion: A reduction in tl1eelectrostatic repulsioll a1nongthe bilayer beadgroupsreduces 1 by increasingtl1espontaneouscurvature of tl1e bilayer. thereby increasingthe membrane defonnation e11ergyassociatedwith chauuel formation.
P-u-20
ROLE OF ACliW FHWPHOWW IN SUBSET STRF# OF B'Xib'RM TRANSLOCAT%ONENLCQ@
VAN RAALTE AU.,DUNJJJPF B. lle!pmmtofBiachemiahyoFMernbnraes,rnstitutc of Biomembnmes,Utnxht University(NL)
l+lqme:Ihc~Eapueaccdependenttmns~n ofprepmeinsacmssthecytop~~caneis dilectiy propoational to the aawunt of acidic phospholipidsm However, it is u@mown in whi&stagesoftheprocesstheseacidic&idsafe achlallyirlvolved Methods: Differart steps of the tm&oWon of proOmpa iota inveztedianer-membfanevesicltscan be amstcd by manipuluing the pmf and ATT cOOC4ZlltntiolL
Rcaults:Aniaremradirte.lepmsen- tl-ado&on of haIfoftIGpoiypqidecha&accumuIates@~ amowltsiRveaickswith a wild-type lipid composition or with a lowered content of PG. However, in the mutaat vesiclesthe A’I’P driven is s&gly re&c& conciusions:lbere PreliiIliajuylwwlts suggestthat acidic lipids stimulate late stage4of Entneiocation probably Py tb& iatarorioa’ with SacA. In futme earlier~intcnnedirt#lwillbestucuedsnd morevaliadouslllmembnane lipid compositionwiIl be Used.
121
GRAMlClDli CHANNELFUNCTION ANDL&PlDCURVATURE MAER AM.. LUNDBAEK JA., PROVIDENCE LL., ANDERSENOS. Dept. of F’hysidogy ad Biophysics. Medic+ College, New York, USA
Cornell
University
Purpose: We tested the relatio11betweeu the lipid molecular shapeat1d the 1nembraue defonnatiou energy. The bg-amicidincbaunel ftuiction varies wit11the spontaneouscurvature of the bilayer, which can be altered by changes in [I-I+], [Ca”] and ionic strengtlth. Methods: Single channelexperilnents were doue using the bilayer puucl1(Audersen, 1983). Results: DecreasiugpH fro1118 to 3 has 110 effect on conductance(8) but reducestl1e averageduratio11(T) and the channel fonni11g potency. Iucreasing[Na’] from 0. I M to I M has no effect on g but decreases‘I. Increasi11g [Ca”] from 3nM to ImM decreasesg and T. Conclusion: A reduction in tl1eelectrostatic repulsioll a1nongthe bilayer beadgroupsreduces 1 by increasingtl1espontaneouscurvature of tl1e bilayer. thereby increasingthe membrane defonnation e11ergyassociatedwith chauuel formation.
P-u-20
ROLE OF ACliW FHWPHOWW IN SUBSET STRF# OF B'Xib'RM TRANSLOCAT%ONENLCQ@
VAN RAALTE AU.,DUNJJJPF B. lle!pmmtofBiachemiahyoFMernbnraes,rnstitutc of Biomembnmes,Utnxht University(NL)
l+lqme:Ihc~Eapueaccdependenttmns~n ofprepmeinsacmssthecytop~~caneis dilectiy propoational to the aawunt of acidic phospholipidsm However, it is u@mown in whi&stagesoftheprocesstheseacidic&idsafe achlallyirlvolved Methods: Differart steps of the tm&oWon of proOmpa iota inveztedianer-membfanevesicltscan be amstcd by manipuluing the pmf and ATT cOOC4ZlltntiolL
Rcaults:Aniaremradirte.lepmsen- tl-ado&on of haIfoftIGpoiypqidecha&accumuIates@~ amowltsiRveaickswith a wild-type lipid composition or with a lowered content of PG. However, in the mutaat vesiclesthe A’I’P driven is s&gly re&c& conciusions:lbere PreliiIliajuylwwlts suggestthat acidic lipids stimulate late stage4of Entneiocation probably Py tb& iatarorioa’ with SacA. In futme earlier~intcnnedirt#lwillbestucuedsnd morevaliadouslllmembnane lipid compositionwiIl be Used.
121