Translational diffusion in the plasma membrane of sea urchin eggs

[摘要] TranslationaldiffusionintheplasmamembraneofindividualeggcellsfromtheseaurchinspeciesParacentrotuslividushasbeenstudiedbyfluorescencemicrophotolysis(FM).Inordertoprobethelipidphaseofthemembrane,procedureshavebeenworkedoutbywhichthefluorescentanalog3,3′-dioctadecyl-oxatricarbocyanine(C18diO)canbeincorporatedintothemembrane.IntheunfertilizedeggafractionR=0.9ofC18diOwasmobilehavinganapparentdiffusioncoefficientofD=6.0×10−9cm2sec−1.Fifteentotwenty-fiveminutesafterfertilizationRandDwerereducedto0.8and2.7×10−9cm2sec−1,respectively.Inordertostudydiffusionofmembraneproteins,procedureshavebeenworkedoutbywhichthecellsurfacecanbelabeledwithfluorescein-isothiocyanate(FITC).FITCbindstoboththeplasmamembraneandthevitellinelayer.Togetherwiththevitellinelayertwo-thirdsoftheFITC-fluorescencecouldberemovedfromtheeggsurface.Gelelectropherogramsofisolatedeggcorticesshowedvariousproteinbands;however,onlytwooftheproteinbandswerelabeledwithFITC.IntheunfertilizedeggafractionR=0.9oftheFITC-labeledmembraneproteinswasmobilehavinganapparentdiffusioncoefficientofD=35×10−11cm2sem−1.Fiteentotwenty-fiveminutesafterfertilizationRandDwerereducedto0.8and7.0×10−11cm2sec−1,respectively.FITC-labeledproteinsofthefertilizationenvelopewereimmobile.Ourstudieshaveshown(i)thattheeggsurfacecanbefluorescentlylabeledwithoutblockingfertilizationandearlydevelopment,(ii)thattheplasmamembraneofunfertilizedeggsisafluidenvironmentpermittingarapidmovementoflipidsandproteins,and(iii)thatafterfertilizationasubstantialdegreeoflipidandproteinmobilityismaintained.

[学科分类] 生物科学（综合）