Nuclear pores yog ib qho tseem ceeb tshaj plaws ntawm cov khoom hauv lub cev vim lawv koom nrog hauv kev thauj mus los. Txawm hais tias muaj kev nce qib hauv kev tshawb fawb txog roj ntsha, tsis yog txhua cov lus nug txog cov qauv no tau tshawb pom tag nrho. Qee cov kws tshawb fawb ntseeg hais tias qhov kev ua haujlwm ntawm nuclear pore complex tuaj yeem raug ntaus nqi rau cov cell organelles raws li qhov tseem ceeb ntawm kev ua haujlwm thiab cov txheej txheem nyuaj.
Nuclear plhaub
Ib yam ntxwv ntawm cov hlwb eukaryotic yog qhov muaj cov nucleus, uas nyob ib puag ncig los ntawm daim nyias nyias uas cais nws ntawm cytoplasm. Lub daim nyias nyias muaj ob txheej - sab hauv thiab sab nrauv, interconnected los ntawm ib tug loj tus naj npawb ntawm pores.
Qhov tseem ceeb ntawm lub hnab ntawv nuclear yog qhov siab heev - nws tso cai rau koj los txiav txim siab cov txheej txheem ntawm cov protein synthesis thiab nucleic acids tsim nyog los tswj cov haujlwm ua haujlwm ntawm cov noob. Lub membrane tswj cov txheej txheem ntawm kev thauj khoom sab hauv, mus rau hauv cytoplasm, thiab vice versa. Nws kuj yog cov qauv pob txha uas txhawb nqa cov duab ntawm lub nucleus.
Nruab nrab ntawm sab nrauv thiab sab hauv daim nyias nyias yog qhov chaw perinuclear, qhov dav ntawm 20-40 nm. Sab nraud, lub hnab ntawv nuclear zoo liob txheej hnab. Lub xub ntiag ntawm qhov pores hauv nws cov qauv yog qhov sib txawv tseem ceeb ntawm cov qauv no thiab cov zoo sib xws hauv mitochondria thiab plastids.
Structure of nuclear pores
Channels yog perforations txog 100 nm hauv txoj kab uas hla, hla tag nrho lub hnab ntawv nuclear. Hauv ntu ntu, lawv yog tus cwj pwm los ntawm cov duab ntawm lub polygon nrog symmetry ntawm qhov kev txiav txim thib yim. Cov tshuaj-permeable channel yog nyob rau hauv qhov chaw. Nws tau sau nrog cov txheej txheem globular complex (nyob rau hauv daim ntawv ntawm ib co coil) thiab fibrillar (nyob rau hauv daim ntawv ntawm ib tug twisted xov) cov qauv uas tsim ib tug central granule - ib tug "plug" (los yog ib tug transporter). Nyob rau hauv daim duab hauv qab no, koj tuaj yeem kawm kom meej tias lub pore nuclear yog dab tsi.
Kev kuaj xyuas microscopic ntawm cov qauv no qhia tau hais tias lawv muaj cov qauv sib luag. Fibrillar outgrowths ncua ob sab nraud, rau hauv cytoplasm, thiab sab hauv, mus rau lub nucleus (filaments). Lub tom kawg tsim ib hom pob tawb (hu ua "basket" nyob rau hauv cov ntaub ntawv txawv teb chaws). Nyob rau hauv cov pore passive, pob tawb fibrils kaw cov channel, thaum nyob rau hauv lub active pore lawv tsim ib tug ntxiv tsim txog 50 nm inch. Lub nplhaib ntawm sab ntawm lub cytoplasm muaj 8 granules interconnected zoo li hlaws dai ntawm ib txoj hlua.
Tag nrho ntawm cov perforations nyob rau hauv lub plhaub ntawm lub nucleus yog hu ua complex ntawm nuclear pores. Yog li, biologists hais txog kev sib cuam tshuam ntawm tus kheej lub qhov, ua haujlwm raws li ib qho kev sib koom tes zoo.
Lub nplhaib sab nraud txuas nrog lub hauv nruab nrab conveyor. Cov eukaryotes qis (lichens thiab lwm yam) tsis muaj cytoplasmicthiab nucleoplasmic rings.
qauv nta
Cov qauv thiab kev ua haujlwm ntawm cov pores nuclear muaj cov yam ntxwv hauv qab no:
- Channels muaj ntau daim ntawv luam txog li 30-50 nucleoporins (rau tag nrho txog 1000 proteins).
- Qhov loj ntawm qhov sib txawv ntawm 44 MDa hauv qis dua eukaryotes mus rau 125 MDa hauv vertebrates.
- Nyob rau hauv tag nrho cov kab mob (tib neeg, noog, tsiaj reptiles thiab lwm yam tsiaj), nyob rau hauv tag nrho cov hlwb, cov qauv no yog teem nyob rau hauv ib tug zoo xws li txoj kev, uas yog, pore complexes yog ib tug nruj kev saib xyuas system.
- Cov khoom ntawm nuclear complexes muaj cov qauv subunit, vim lawv muaj cov yas siab.
- Txoj kab uas hla ntawm lub hauv paus channel sib txawv ntawm 10-26 nm, thiab qhov siab ntawm qhov pore complex yog li 75 nm.
Qhov chaw ntawm lub qhov hws ntawm qhov chaw deb ntawm qhov chaw tsis sib luag. Cov kws tshawb fawb ntaus nqi qhov no rau ntau yam kev tswj hwm ntawm kev thauj mus los ntawm cov theem pib ntawm kev loj hlob ntawm tes. Nws kuj tseem xav tias txhua qhov pores yog cov qauv thoob ntiaj teb thiab xyuas kom muaj kev txav ntawm cov molecules ob qho tib si rau hauv cytoplasm thiab nyob rau hauv qhov sib txawv. Nuclear pore complexes kuj muaj nyob rau hauv lwm cov membrane-cov kabmob ntawm tes, tab sis nyob rau hauv tsawg zaus (reticulum, fenestrated cytoplasmic membranes).
Ntau qhov pores
Lub ntsiab tseem ceeb uas txiav txim siab tus naj npawb ntawm cov pores nuclear yog cov kev ua hauv metabolic hauv cell (qhov siab dua, ntau dua.tus naj npawb ntawm tubules). Lawv cov concentration nyob rau hauv lub thickness ntawm daim nyias nyias tuaj yeem hloov tau ob peb zaug thaum lub sijhawm sib txawv ntawm kev ua haujlwm ntawm lub hlwb. Thawj qhov nce ntawm cov pores tshwm sim tom qab kev faib tawm - mitosis (thaum lub sijhawm rov tsim kho ntawm nuclei), thiab tom qab ntawd thaum lub sijhawm DNA loj hlob.
Ntau hom tsiaj muaj tus lej sib txawv. Nws kuj nyob ntawm qhov chaw uas tus qauv coj mus. Yog li, nyob rau hauv tib neeg cov ntaub so ntswg kab lis kev cai, muaj txog 11 pcs/µm 2, thiab nyob rau hauv ib tug tsis paub qab hau xenopus qav qe cell - 51 pcs/µm 2. Qhov nruab nrab, lawv qhov ceev sib txawv ntawm 13-30 daim / µm 2.
Kev faib tawm ntawm cov pores ntawm lub plhaub ntawm lub plhaub yog yuav luag sib xws, tab sis nyob rau hauv qhov chaw uas cov khoom ntawm chromosomes ze rau daim nyias nyias, lawv cov concentration txo qis heev. Cov eukaryotes qis dua tsis muaj lub zog fibrillar network nyob rau hauv daim nyias nyias, yog li lub qhov hws tuaj yeem txav mus rau hauv daim nyias nyias, thiab lawv qhov ceev hauv ntau qhov chaw sib txawv heev.
Functions
Lub luag haujlwm tseem ceeb ntawm lub cev qhov pore complex yog passive (diffusion) thiab nquag (yuav tsum tau them nqi hluav taws xob) hloov ntawm cov molecules los ntawm daim nyias nyias, uas yog, kev sib pauv ntawm cov khoom ntawm cov cell nucleus thiab cytoplasm. Cov txheej txheem no tseem ceeb heev thiab yog tswj hwm los ntawm peb lub tshuab uas muaj kev sib cuam tshuam nrog ib leeg:
- ib qho nyuaj ntawm cov tshuaj lom neeg lom neeg-regulators hauv cov nucleus thiab cytoplasm - importin α thiab β, Ran-protein, guanosine triphosphate (purine nucleotide) thiab lwm yam inhibitors thiab activators;
- nucleoporins;
- cov khoom sib xyaw ntawm cov ntxeem tau nuclear complex, uas muaj peev xwm hloov tau lawv cov duab thiab xyuas kom cov khoom hloov mus rau qhov raug.
Cov protein uas tsim nyog rau kev ua haujlwm ntawm lub hauv paus chiv keeb los ntawm cytoplasm los ntawm cov pores nuclear, thiab ntau hom RNA raug tawm mus rau qhov sib txawv. Lub pore complex tsis tsuas yog ua tiav cov khoom siv thauj khoom nkaus xwb, tab sis kuj ua haujlwm raws li tus neeg txheeb xyuas uas "paub" qee cov molecules.
Passive hloov pauv tshwm sim rau cov tshuaj uas nws qhov hnyav molecular qis (tsis ntau tshaj 5∙10 3 Yog). Cov khoom xws li ions, suab thaj, cov tshuaj hormones, nucleotides, adenosine triphosphoric acid, uas koom nrog hauv kev sib pauv zog, nkag mus rau hauv lub nucleus. Qhov siab tshaj plaws ntawm cov proteins uas tuaj yeem nkag mus rau hauv lub qhov hws mus rau hauv lub nucleus yog 3.5 nm.
Thaum lub sijhawm sib txuas ntawm tus ntxhais DNA molecule, kev thauj khoom mus txog qhov kawg ntawm kev ua haujlwm - 100-500 molecules los ntawm 1 nuclear pore hauv 1 feeb.
YPore proteins
Channel cov ntsiab lus yog cov protein ntau. Cov proteins ntawm no complex hu ua nucleoporins. Lawv tau sau nyob rau hauv kwv yees li 12 subcomplexes. Conventionally, lawv muab faib ua peb pawg:
- cov khoom sib xyaw nrog cov txheej txheem rov ua kom pom tau los ntawm cov khoom siv biochemical;
- tsis muaj ib ntus;
- cov proteins uas muaj nyob hauv thaj tsam ntawm daim nyias nyias uas tsim cov pore, lossis hauv qhov pore nws tus kheej hauv qhov chaw nruab nrab ntawm cov txheej txheem ntawm lub hnab ntawv nuclear.
Kev tshawb fawb tau pom tias nucleoporins tuaj yeem tsim taues complexes, suav nrog txog li 7 proteins, thiab tseem muaj kev koom tes ncaj qha rau hauv kev thauj khoom. Qee tus ntawm lawv tuaj yeem khi ncaj qha rau cov molecules txav los ntawm lub qhov hws nuclear.
Export cov tshuaj mus rau cytoplasm
Tib qhov pore tuaj yeem koom nrog hauv ob qho kev tshem tawm thiab ntshuam cov tshuaj. Qhov rov qab txhais ntawm RNA los ntawm cytoplasm mus rau hauv lub nucleus tsis tshwm sim. Nuclear complexes lees paub cov cim xa tawm (NES) nqa los ntawm ribonucleoproteins.
NES-ib ntu ntawm cov khoom siv taw qhia yog ib qho nyuaj ntawm cov amino acids thiab cov proteins, uas, tom qab raug tshem tawm ntawm lub nucleus mus rau hauv cytoplasm, dissociate (tawg mus rau hauv cov khoom sib cais). Yog li ntawd, cov khoom zoo sib xws tau qhia rau hauv cytoplasm tsis nkag mus rau hauv lub nucleus.
txheej txheem ntawm mitosis
Thaum lub sijhawm sib faib ntawm tes (mitosis), lub cev nqaij daim tawv yog "dismantled". Yog li, complexes nrog ib qho hnyav molecular ntawm 120 mDa decompose rau hauv subcomplexes ntawm 1 mDa txhua. Tom qab qhov kawg ntawm kev faib, lawv rov sib sau ua ke. Nyob rau hauv cov ntaub ntawv no, lub nuclear pores tsis tsiv mus nyob nyias, tab sis nyob rau hauv arrays. Qhov no yog ib qho ntawm cov pov thawj hais tias lub nuclear pore complex yog ib qho kev sib koom tes zoo.
Cov ruptured membrane hloov mus ua ib pawg npuas uas nyob ib puag ncig ntawm cov tub ntxhais hauv lub sijhawm interphase. Hauv metaphase, thaum cov chromosomes tuav hauv lub dav hlau equatorial, cov ntsiab lus no raug thawb mus rau thaj tsam peripheral ntawm tes. Thaum kawg ntawm anaphase, pawg no pib hu rau chromosomes thiab kev loj hlob pib.rudiments ntawm nuclear membrane.
Npaj mus ua vacuoles, uas maj mam ntim cov chromosomes. Tom qab ntawd lawv sib koom ua ke thiab laj kab tawm ntawm tus tshiab interphase nucleus los ntawm cytoplasm. Cov pores tau tshwm sim nyob rau theem ntxov, thaum kaw lub plhaub tseem tsis tau tshwm sim.
