Intermediate filaments yog cov yam ntxwv ntawm cov hlwb eukaryotic. Lawv yog cov self-assembled thiab chemically resistant. Cov qauv thiab kev ua haujlwm ntawm cov filaments nruab nrab yog txiav txim siab los ntawm cov yam ntxwv ntawm cov ntawv cog lus hauv cov protein molecules. Lawv ua hauj lwm tsis tau tsuas yog tsim lub cell scaffold, tab sis kuj xyuas kom meej kev sib cuam tshuam ntawm organelles.
Kev piav qhia dav dav
Filaments yog filamentous protein cov qauv uas koom nrog hauv kev tsim cov cytoskeleton. Raws li txoj kab uas hla lawv muab faib ua 3 chav kawm. Intermediate filaments (IF) muaj qhov nruab nrab ntu ntu ntawm 7-11 nm. Lawv tuav ib qho chaw nruab nrab ntawm microfilaments Ø5-8 nm thiab microtubules Ø25 nm, uas lawv tau txais lawv lub npe.
Muaj 2 hom qauv no:
- Lamine. Lawv nyob hauv qhov tseem ceeb. Txhua tus tsiaj muaj laminar filaments.
- YCytoplasmic. Lawv nyob hauv cytoplasm. Muaj nyob rau hauv nematodes, mollusks, vertebrates. Nyob rau tom kawg, qee hom hlwb yuav tsis tuaj (piv txwv li, hauv cov hlwb glial).
Qhov chaw
Intermediate filaments yog ib qho ntawm cov ntsiab lus tseem ceeb ntawm cytoskeleton ntawm cov kab mob nyob uas nws cov hlwb muaj cov nuclei (eukaryotes). Prokaryotes kuj muaj cov analogues ntawm cov qauv fibrillar. Lawv tsis pom nyob rau hauv cov nroj tsuag.
Feem ntau ntawm cov filaments nyob rau hauv thaj tsam perinuclear thiab cov pob ntawm fibrils, uas nyob hauv qab cov plasma membrane thiab txuas mus rau qhov chaw mus rau cov npoo ntawm cov hlwb. Muaj ntau yam tshwj xeeb ntawm lawv nyob rau hauv cov tsiaj uas raug kev ntxhov siab - hauv cov leeg nqaij, epithelial, thiab tseem nyob hauv cov hlwb ntawm cov hlab ntsha.
Protein types
Raws li kev tshawb fawb qhia, cov proteins uas tsim cov filaments nruab nrab yog qhov txawv nyob ntawm seb hom cell thiab theem ntawm lawv qhov sib txawv. Txawm li cas los xij, lawv txhua tus muaj feem cuam tshuam.
Cov protein nruab nrab nruab nrab yog muab faib ua 4 hom:
- Keratins. Lawv tsim cov polymers los ntawm ob hom subtypes - acidic thiab nruab nrab. Qhov hnyav molecular ntawm cov tebchaw no nyob ntawm 40,000-70,000 amu. m. Nyob ntawm cov ntaub so ntswg, tus naj npawb ntawm ntau hom heterogeneous ntawm keratins tuaj yeem ncav cuag ntau kaum. Lawv tau muab faib ua 2 pawg raws li isoform - epithelial (feem ntau ntau) thiab horny, uas ua rau cov plaub hau, horns, rau tes thiab plaub tsiaj.
- Hauv hom thib ob, 3 hom proteins sib xyaw ua ke, muaj yuav luag tib lub cev hnyav (45,000-53,000 amu). Cov no suav nrog: vimentin (cov ntaub so ntswg sib txuas, squamous hlwb,nyob rau hauv cov hlab ntsha ntawm cov hlab ntsha thiab lymphatic; cov qe ntshav) desmin (cov leeg nqaij); peripherin (peripheral thiab central neurons); glial fibrillar acidic protein (cov protein tshwj xeeb hauv hlwb).
- Neurofilament proteins pom nyob rau hauv neurites, cylindrical txheej txheem uas nqa impulses ntawm paj hlwb.
- Cov proteins ntawm nuclear lamina uas underlies lub nuclear membrane. Lawv yog cov thawj coj ntawm txhua tus PFs.
Cov filaments nruab nrab tuaj yeem muaj ntau hom ntawm cov khoom saum toj no.
Properties
Cov yam ntxwv ntawm PF yog txiav txim siab los ntawm lawv cov yam ntxwv hauv qab no:
- coob tus ntawm polypeptide molecules hauv ntu ntu;
- muaj zog hydrophobic kev sib cuam tshuam uas ua lub luag haujlwm tseem ceeb hauv kev sib dhos ntawm macromolecules hauv daim ntawv ntawm twisted supercoil;
- tsim ntawm tetramers nrog kev sib cuam tshuam electrostatic siab.
Vim li ntawd, cov kab nruab nrab nruab nrab tau txais cov khoom ntawm txoj hlua sib tw uas muaj zog - lawv khoov zoo, tab sis tsis tawg. Thaum kho nrog cov tshuaj reagents thiab muaj zog electrolytes, cov qauv no yog qhov kawg mus rau hauv kev daws, uas yog, lawv muaj cov tshuaj lom neeg ruaj khov. Yog li, tom qab ua tiav denaturation ntawm cov protein molecules hauv urea, cov filaments tuaj yeem sib sau ua ke. Proteins qhia los ntawm sab nraud yog sib xyaw ua ke sai sai rau hauv cov qauv uas twb muaj lawm ntawm cov tebchaw no.
qauv
Los ntawm lawv cov qauv, nruab nrab filaments tsis-branchingpolymers uas muaj peev xwm ntawm ob qho tib si tsim ntawm macromolecular compounds thiab depolymerization. Lawv cov qauv tsis ruaj khov pab cov hlwb hloov lawv cov duab.
Txawm hais tias cov filaments muaj ntau haiv neeg raws li hom proteins, lawv muaj tib txoj kev npaj. Nyob rau hauv nruab nrab ntawm cov molecules muaj ib tug alpha helix, uas muaj cov duab ntawm ib sab tes xis helix. Nws yog tsim los ntawm kev sib cuag ntawm cov qauv hydrophobic. Nws cov qauv muaj 4 ntu kauv sib cais los ntawm ntu luv uas tsis yog kauv.
Ntawm qhov kawg ntawm alpha helix yog cov npe nrog cov qauv tsis muaj qhov kawg. Lawv ua lub luag haujlwm tseem ceeb hauv kev sib dhos filament thiab kev cuam tshuam nrog cell organelles. Lawv qhov loj me thiab cov protein sib txawv sib txawv ntawm ntau hom IF hom.
tsim cov protein
Cov khoom siv hauv tsev tseem ceeb rau PF yog cov dimers - cov molecules complex muaj li ntawm ob qho yooj yim. Feem ntau lawv suav nrog 2 cov protein sib txawv txuas nrog cov qauv pas nrig.
Cov cytoplasmic hom filaments muaj cov dimers uas tsim cov xov 1 thaiv tuab. Txij li thaum lawv yog parallel tab sis nyob rau hauv opposite direction, tsis muaj polarity. Cov dimeric molecules tom qab ntawd tuaj yeem tsim ntau dua.
Functions
Lub luag haujlwm tseem ceeb ntawm cov filaments nruab nrab yog raws li hauv qab no:
- kom ntseeg tau lub zog ntawm cov hlwb thiab lawv cov txheej txheem;
- kev hloov pauv rau cov kev ntxhov siab;
- koom nrogkev sib cuag uas muab kev sib txuas ntawm cov hlwb (epithelial thiab cov leeg nqaij);
- intracellular faib ntawm cov protein thiab organelles (localization ntawm Golgi apparatus, lysosomes, endosomes, nuclei);
- kev koom tes hauv kev thauj lipid thiab kev taw qhia ntawm cov hlwb.
PF kuj cuam tshuam rau kev ua haujlwm mitochondrial. Raws li kev sim ntawm cov nas pom, hauv cov tib neeg uas tsis muaj desmin gene, cov txheej txheem intracellular ntawm cov organelles raug cuam tshuam, thiab cov hlwb lawv tus kheej raug programmed rau lub neej luv. Vim li ntawd, cov ntaub so ntswg noj cov pa oxygen txo.
Ntawm qhov tod tes, qhov muaj qhov nruab nrab ntawm cov filaments ua rau txo qis hauv mitochondrial mus. Yog hais tias vimentin yog tsim los rau hauv lub cell, ces IF network yuav rov qab tau.
Tshuaj Tseem Ceeb
Kev ua txhaum hauv kev sib txuas, sib sau thiab cov qauv ntawm PF ua rau muaj qhov tshwm sim ntawm qee yam kab mob:
- Tsim cov hyaline tee hauv cytoplasm ntawm daim siab hlwb. Hauv lwm txoj kev, lawv hu ua Mallory lub cev. Cov qauv no yog IF proteins ntawm hom epithelial. Lawv raug tsim los ntawm kev haus dej cawv ntev ntev (mob cawv kab mob siab), nrog rau kev ua txhaum ntawm cov txheej txheem metabolic hauv thawj kab mob siab hepatocellular (hauv cov neeg mob uas muaj kab mob siab B thiab cirrhosis), nrog rau cov kua tsib nyob rau hauv daim siab thiab lub gallbladder. Alcoholic hyaline muaj cov khoom siv tshuaj tiv thaiv kab mob, uas ua rau kev txhim kho ntawm cov kab mob pathology.
- Thaum cov noob hloov pauv,Lub luag haujlwm rau kev tsim cov keratins, kab mob ntawm daim tawv nqaij tshwm sim - epidermolysis bullosa. Nyob rau hauv rooj plaub no, muaj kev ua txhaum ntawm qhov txuas ntawm txheej txheej ntawm daim tawv nqaij mus rau hauv qab daus daim nyias nyias uas cais nws los ntawm cov ntaub so ntswg. Yog li ntawd, kev yaig thiab npuas yog tsim. Cov tawv nqaij ua rau rhiab heev rau qhov kev puas tsuaj me ntsis.
- Tsim cov plaques senile thiab neurofibrillary tangles hauv hlwb hlwb hauv Alzheimer's tus kab mob.
- Qee yam ntawm cardiomyopathy cuam tshuam nrog ntau dhau ntawm PF.
Peb cia siab tias peb tsab xov xwm teb tag nrho koj cov lus nug.
