Operon - dab tsi yog qhov no?

была впервые предложена Ж. Моно и Ф. Жакобом. Operon qauv thawj npaj los ntawm J. Monod thiab F. Yakhauj. Nyob rau hauv 1961 lawv soj ntsuam cov txheej txheem uas txuam nrog rau txoj kev loj hlob ntawm E. coli hlwb. Nyob rau hauv kev peb kawm mechanisms tswj DNA feem encoding lub mis nyuj qab zib (lactose).

piav qhia

Monod thiab Yakhauj npaj ib txwm co-ordinated tswj ntawm lub yam ntxwv seem ntawm DNA. Lub zaum muab nws lub npe "operon". схемы следующий. Lub hauv paus ntsiab lus ntawm cov lag luam ntawm lub Circuit Court yog raws li nram no. Kev kho pab pawg neeg ntawm DNA sequences encoding polypeptides uas zoo txuam nrog txhua lwm yam operatively tshuaj los ntawm ob ntsiab. Tus thawj yog cov xws li, thiab lub thib ob - tus neeg teb xov tooj. Cov yav tas yog sawv cev nucleotide ib theem zuj zus nyob ib sab mus tswj yam ntxwv feem. Yog hais tias lub protein-compressor, nws ua raws li cov neeg teb xov tooj yuav thaiv DNA transcription units ua raws li ib tug tswj cov khoom. Qhov no, nyob rau hauv lem, yog ib tug yuavtsum tau kawm uantej rau hauv lub tsim ntawm steric obstacles rau RNA polymerase compound rau ib tug feem ntawm lub promoter. Cov yav tas yog tsim nyog los pib transcription. Lwm yam uas yuav tsum tau cov ntaub ntawv, yog hais tias tus regulator ua apoinduktor. Nyob rau hauv no qhov teeb meem, nws twb kev txuas mus rau lub teb xov tooj yuav tsim tej yam kev mob rau lub transcription.

tseem

последовательность ДНК, которая состоит из тесно сцепленных кодирующих участков, промотора и оператора. Operon - ib tug DNA sib liag uas yog ua los ntawm zoo txuas coding cheeb tsam, pab txhawb thiab teb xov tooj. Tswj lub caij tej zaum yuav positioned tom ntej no mus rau nws los yog nyob rau ib tug tej yam kev ncua deb ntawm nws. Cov neeg teb xov tooj yog feem ntau ntawm cov yam ntxwv chaw thiab pab txhawb. Muaj cov mus koom tsis molecular tshuaj, uas yuav tsum tau tswj operon. в частности, эффекторы, которые являются индукторами или крепрессорами структурных участков, включенных в схему. Qhov no, nyob rau hauv particular, tus effectors uas yog inducers los yog krepressorami ntxwv seem muaj nyob rau hauv lub Circuit Court.

kev faib

Yog ntxias los yog repressed operon. зависит от характера влияния на их деятельность молекул-эффекторов. Nws yog nyob ntawm qhov xwm ntawm tej yam rau lawv cov kev ua ntawm effector molecules. Peb ntxias lug nws koom lub repressor los thaiv cov hlab losis tswvyim dabtsi rau tus neeg tsav tsheb. Raws li, muaj obstacles rau lub transcription ntawm lub yam ntxwv seem. называется негативной. Tej kev cai no yog hu ua tsis zoo operons. Txawm li cas los, tus qauv yuav tsum ntxias los ntawm lub zoo tswj. Nyob rau hauv cov ntaub ntawv no, lub effector uake mus rau ib tug ntxawg protein molecule, activating nws apoinduktor. Koom lub xov tooj, nws enables cov transcription. Cov kev tswj hom ua thiab hwm repressed lug. Yog hais tias qhov tsis zoo cai, effector, kuj ua corepressor, kev cob cog rua nrog ib tug tsaug zog repressor thiab activates nws. Raws li ib tug tshwm sim, lub tom kawg nreg lub peev xwm los dock nrog tus neeg tsav tsheb, yog li thaiv cov hlab transcription. Yog hais tias qhov zoo tswj, losis tswvyim dabtsi tshwm sim nrog active apoinduktorom. Qhov no complex yuav tsis tau kev cob cog rua rau lub teb xov tooj. Thiaj li, yam ntxwv feem tsis transcribed.

tshawb pom

Nyob rau hauv qhov tsis zoo tswj, yog li effector uake lub repressor, ua inactivation lossis ua kom. Raws li, ntxias los yog repressed transcription ntawm lub operon. Nyob rau hauv cov ntaub ntawv ntawm ib tug zoo tswj, kev twb kev txuas yog los ua kom apoinduktoru. Qhov no txoj kev tso cai los yog blocks transcription. Cov nyob rau hauv daim ntawv uas acquires apoinduktor thaum uas txuas mus rau lub effector.

Tus qauv ntawm lub operon E.coli

Nyob rau hauv E. coli muaj ib tug qauv muaj lub peev xwm los ferment lactose. Nws muaj xws li cov neeg pab txhawb thiab teb xov tooj peb yam ntxwv DNA feem. Coding raug gengalaktozidaza enzymes galaktozidpermeaza, tiogalaktozidtransatsetilaza. Rau txhua ntawm lawv nws muaj nws tus kheej noob. Lub operon muaj xws li feem Lac Z, Lac A, Lac Y. keeb kwm encodes gengalaktozidazu catalyzing lub lactose rau piam thaj thiab galactose. Lac Y ua num ua ke nrog galaktozidpermeazoy. Qhov no enzyme muab cov thauj ntawm txawv suab thaj. Lac A encodes tiogalaktozidtransatsetilazu. Nws lub luag hauj lwm, tab sis, yog tsis tseeb nyob rau hauv tus txheej txheem ntawm pov ntawm cov mis nyuj qab zib. Feem ntau, tag nrho cov ntawm cov proteins nyob rau hauv lub hlwb ntawm Escherichia coli nyob rau hauv txoj lw nyiaj. Txawm li cas los, thaum zus nyob rau hauv nws cov ib puag ncig, nyob rau lub ib carbon thiab lub zog qhov chaw ua lactose, enzymes tooj hlob 1000 lub sij hawm.

constitutive synthesis

включает в себя структурный участок lac 1. Им кодируется белок-репрессор. Lactose operon muaj xws li ib tug yam ntxwv feem Lac 1. Lawv encoded repressor protein. Nyob rau hauv lub active lub xeev, nws yog ib tug tetramer, uas yog tsim nyob rau ntawm plaub luam feem Lac 1 - ib tug polypeptide muaj ib tug 360 amino acids. Hlwb nrog kev hloov nyob rau hauv no noob nyob rau synthesis ntawm constitutive cov nqaijrog encoded Lac Z, Y thiab A. Nyob rau hauv cov ntaub ntawv no, qhov no yog tau yog hais tias muaj yog tsis tsuas change nyob rau hauv lub repressor, tab sis nyob rau hauv cov nqe lus. Tej kev pauv hloov yeej ib txwm cis-hom. Qhov no yog vim lub fact tias cov neeg teb xov tooj, raws li txwv mus rau ib tug repressor, yuav los ntawm lub tau ntawm transcription tsuas yog thaum nyob nyob zoo sib thooj rau cov neeg pab txhawb. Yog hais tias tam sim no nyob rau hauv lub cell-ntxias tebchaw, lawv tuaj nrog ib tug neeg teb xov tooj nyob rau hauv cov kev sib tw rau lub repressor molecule.

inductors

Lawv tej zaum yuav txawv sib txuas. Lactose ua ob yam li ib inducer thiab raws li ib tug substrate. Nyob rau hauv ib txwm hlwb thiab nyob rau hauv lub qhaj ntawv ntawm ntxias residual enzyme ua si ntawm lub tebchaw muab tau ntawm allergic ntawm lactose hauv me nyiaj. Raws li ib tug tshwm sim ntawm cov tshuaj tiv thaiv catalytic lactose yog hloov mus rau hauv allolactose. Nws, nyob rau hauv lem, binds mus rau lub repressor thiab provokes nws los ntawm raug kaw los ntawm lub xov tooj. Qhov no tso cai rau lub RNA polymerase mus rau lub promoter khoom. Qhov no yuav pib lub transcription ntawm Lac Z, A thiab Y. tebchaw kuj tsuas yog raws li inductors, IPTG thiab TMG yog siv los kawm txog cov kev tswj ntawm ib tug lactose operon.

Affirmative txiav txim hais

Lawv qhia kom paub yog tshwm sim los diauksiey. Lub essence ntawm no phenomenon yog hais tias lub siv ntawm lactose pib tsuas yog tom qab siv tag nrho muaj piam thaj nyob rau hauv lub nruab nrab. Diauksiya - ib qho ntawm lub ces catabolite tsuj. Cov nyhuv no yog lub npe hu los ntawm zib 40s. lub xyoo pua xeem. Nws yog qhia nyob rau hauv E. coli cev tsis catabolize carbohydrates txawv nyob rau hauv lub xub ntiag ntawm qabzib. Nws, nyob rau hauv lem, ua raws li ib tug ntau npaum chaw ntawm lub zog.

Lub mechanism ntawm cov nyhuv

Nws yuav decipher Pastan thiab Perlman. Lawv nrhiav tau ob tug hais tias yog transcribed lac- operon. небольшая молекула-эффектор – цАМФ (циклический аденозинмонофосфат) и белок-активатор катаболизма САР. Qhov no yog ib tug me me molecule effector - Camp (cyclic adenosine monophosphate) thiab activator protein catabolism ATS. Nyob rau hauv eukaryotes, thawj ua raws li ib tug neeg tuaj daws kho ntawm hormone kev txiav txim. Nws pom hais tias qhov sib ntxiv ntawm lub yeej rog rau E. coli hlwb, loj hlob nyob rau hauv ib qho chaw uas muaj cov qabzib, decelerates nws ceev, tab sis nws yog muab tshem tawm catabolic tsuj. Qhov no, nyob rau hauv lem, ua tau ntawm cov kev qhia ntawm Lac-operon nyob rau hauv lub simultaneous xub ntiag ntawm piam thaj thiab lactose. Tom qab ib co sij hawm tau ib tug rov qab sib raug zoo. Cov kev ua ntawm lub enzyme Camp synthesis yog inhibited by qabzib.

xaus

Transcription ntawm lub operon yog nyob rau hauv dual tswj - tsis zoo thiab zoo. CAP-Camp complex enables cov RNA polymerase mus txuas rau lub template DNA ua ntej ua. Tam sim no, zaum deciphered lub tiav nucleotide saw ntawm lub ntxawg cheeb tsam ntawm lub Lac-operon, nyob rau hauv uas muaj yog ib tug neeg teb xov tooj thiab pab txhawb. Ntxiv mus, nyob rau hauv 1969, nws tau faib nws cov ntshiab DNA fragment muaj Lac 1 pab txhawb thiab tag nrho neeg teb xov tooj ua ntu zus, Lac Z thiab Lac Y. fragment Nyob rau hauv txoj kev tshawb no nws pom hais tias ib tug tseem ceeb luag hauj lwm nyob rau hauv lub sis ntawm multimeric cov nqaijrog nrog DNA yog symmetrical lug - palindrome . Lub Lac-operon neeg teb xov tooj ntawm lawv tam sim no 26. Nyob rau tib lub sij hawm 14 ntawm lawv yog cov sib txawv things. Txawv chains lawv nyeem ib yam tab sis nyob rau hauv kev coj rov qab. Palindrome nrhiav tau nyob rau hauv lub promoter feem thiab interacting nrog ib tug complex ntawm Camp-CAP.