Flying gait: Yuav ua li cas rau cov protein nyob hauv lub cell

2024 Tus sau: Seth Attwood | [email protected]. Kawg hloov kho: 2023-12-16 16:06

Ntau tus tsis txawm xav tias yuav ua li cas cov txheej txheem zoo kawg nkaus tau tshwm sim hauv peb. Kuv xav kom koj saib ntxiv ntawm lub ntiaj teb microscopic, uas koj tau tswj kom pom tsuas yog nrog qhov tshwm sim ntawm lub cim tshiab tshiab electron microscopes.

Rov qab rau xyoo 2007, cov kws tshawb fawb Nyij Pooj tuaj yeem soj ntsuam hauv lub tshuab ntsuas qhov ua haujlwm ntawm ib qho ntawm "molecular motors" ntawm lub cell nyob - taug kev protein myosin V, uas tuaj yeem txav mus los ntawm cov actin fibers thiab rub cov luj uas txuas rau nws. Txhua kauj ruam ntawm myosin V pib nrog qhov tseeb tias ib qho ntawm nws "sab ceg" (rov qab) yog cais los ntawm actin filament. Tom qab ntawd ob txhais ceg khoov mus rau pem hauv ntej, thiab thawj zaug tig mus rau ntawm "pob khawm" txuas ob txhais ceg ntawm cov molecule, kom txog thaum nws tsoo lub actin filament. Qhov kawg tshwm sim ntawm kev chaotic txav ntawm thawj ceg hloov mus rau kev txiav txim siab nruj heev vim yog qhov chaw ruaj khov ntawm qhov thib ob.

Cia peb kawm paub ntxiv txog qhov no …

… kinesin taug kev zoo li no

Ib qho kev txav txav ua los ntawm cov kab mob uas muaj sia nyob (los ntawm kev txav ntawm chromosomes thaum lub sij hawm faib cell mus rau cov leeg nqaij contractions) yog ua los ntawm kev ua haujlwm ntawm "molecular motors" - protein complexes, qhov chaw uas muaj peev xwm txav tau txheeb ze rau ib leeg. Hauv cov kab mob siab dua, qhov tseem ceeb tshaj plaws ntawm cov molecular motors yog myosin molecules ntawm ntau hom (I, II, III, thiab lwm yam, mus txog rau XVII), uas muaj peev xwm txav mus los ntawm cov actin fibers.

Ntau "molecular motors", suav nrog myosin V, siv lub hauv paus ntsiab lus ntawm kev taug kev. Lawv txav mus rau hauv cov kauj ruam tsis sib xws ntawm kwv yees li qhov ntev, thiab hloov pauv ib lossis lwm qhov ntawm ob "ceg" ntawm cov molecule nyob rau hauv pem hauv ntej. Txawm li cas los xij, ntau cov ntsiab lus ntawm cov txheej txheem no tseem tsis meej.

Cov kws tshawb fawb ntawm Department of Physics, Waseda University hauv Tokyo tau tsim cov txheej txheem uas tso cai rau koj los saib xyuas cov haujlwm ntawm myosin V hauv lub sijhawm tiag tiag hauv lub tshuab tsom. Ua li no, lawv tsim ib qho kev hloov kho myosin V, nyob rau hauv uas cov ceg shafts muaj cov cuab yeej ruaj khov "sticking" rau tubulin microtubules.

Los ntawm kev ntxiv cov seem ntawm microtubules rau cov kev daws teeb meem ntawm kev hloov kho myosin V, cov kws tshawb fawb tau txais ntau qhov chaw nyob rau hauv uas ib daim ntawm microtubule adhered tsuas yog rau ib ceg ntawm myosin V, thaum lwm qhov tseem nyob dawb. Cov complexes khaws cia muaj peev xwm "taug kev" raws cov actin fibers, thiab lawv cov kev txav tuaj yeem raug soj ntsuam, vim tias qhov tawg ntawm microtubules loj dua myosin nws tus kheej, thiab, ntxiv rau, lawv tau sau nrog cov ntawv fluorescent. Nyob rau hauv rooj plaub no, ob txoj kev sim tsim tau siv: nyob rau hauv ib rooj plaub, ib tug actin fiber tau tsau nyob rau hauv qhov chaw, thiab cov kev soj ntsuam tau nqa tawm nyob rau hauv lub zog ntawm ib tug microtubule fragment, thiab nyob rau hauv lub thib ob, ib tug microtubule tau tsau thiab lub zog ntawm ib tug microtubule. Actin fiber ntau tau pom.

Yog li ntawd, qhov "gait" ntawm myosin V tau kawm kom ntxaws (saib thawj daim duab). Txhua kauj ruam pib nrog "rov qab" ceg ntawm myosin cais tawm ntawm actin fiber. Tom qab ntawd txhais ceg, uas tseem txuas nrog lub fiber, leans rau pem hauv ntej sharply. Nws yog lub sijhawm no uas siv lub zog (ATP hydrolysis tshwm sim). Tom qab ntawd, "dawb" ceg (ntsuab ntsuab hauv cov duab) pib dangle chaotically ntawm pob khawm. Qhov no tsis muaj dab tsi ntau tshaj li Brownian tsab ntawv tsa suab. Nyob rau tib lub sijhawm, los ntawm txoj kev, cov kws tshawb fawb tau pom thawj zaug tias pob khawm txuas ob txhais ceg ntawm myosin V tsis txwv lawv cov kev txav txhua. Tsis ntev los sis tom qab, cov ceg ntsuab kov qhov kawg ntawm cov actin filament thiab txuas nws tus kheej rau nws. Qhov chaw uas nws yuav txuas mus rau txoj hlua (thiab yog li qhov ntev stride) yog txiav txim siab tag nrho los ntawm kev ruaj ntseg ntawm ceg xiav.

Hauv qhov kev sim, kev tshawb nrhiav cov actin filament nrog dawb ceg ntawm myosin V siv ob peb vib nas this; Nyob rau hauv lub cell nyob, qhov no tshwm sim sai dua, txij li thaum muaj myosin taug kev yam tsis muaj qhov hnyav ntawm nws ob txhais ceg. Qhov hnyav - piv txwv li, cov hlwv hauv cov hlab ntsha uas nyob ib puag ncig los ntawm daim nyias nyias - tsis txuas rau ob txhais ceg, tab sis mus rau ib feem ntawm cov molecule, uas tau piav qhia tias yog "tail" hauv daim duab.