Ngā operon i roto i te Whakahaere Ira Huakita
Ko te whakahaere ira ko te kaha o ngā pūtau ki te "whakakā" me te "whakaweto" rānei i te whakaaturanga ira ina hiahiatia. I roto i ngā huakita, he mea nui tēnei whakahaere nā te mea e noho ana rātou i roto i ngā taiao e tere hurihuri ana—ka piki ake, ka heke rānei te wātea o ngā matūkai, ka puta ake ngā āhuatanga ahotea, ā, me urupare pai ngā huakita kia ora ai. Ko tētahi ariā matua e whakamārama ana i te whakarite a ngā huakita i te whakaaturanga ira ko te operon. Ka taea e ngā operon te whakahaere i ngā ira maha me ngā mahi e pā ana hei wāhanga kotahi, ka taea ai e ngā huakita te tiaki i te pūngao me te tere ake i ngā urupare urutau.
Te Mārama ki ngā Whakahaere
Ko te operon he wae mahi o te DNA i roto i ngā huakita e tito ana i tētahi rōpū ira hanganga kei roto i tētahi raupapatanga kotahi, ā, e whakaatuhia ngātahi ana i raro i te mana o tētahi huānga whakahaere noa. I te nuinga o te wā, ka puta i ngā ira i roto i tētahi operon tētahi mRNA polycistronic kotahi—ko te tikanga he ngota mRNA kotahi e kawe ana i ngā mōhiohio mō te whakamāori i ngā pūmua maha i te wā kotahi. He rerekē tēnei i te maha o ngā rauropi eukaryotic, e whakaputa ana i te mRNA monocistronic (kotahi mRNA mō tētahi pūmua kotahi).
I te tuatahi i rongonuihia te ariā o ngā operon e François Jacob rāua ko Jacques Monod mā roto i ngā rangahau mō Escherichia coli (E. coli), inā koa ko te lac operon, e whakahaere ana i te whakamahinga o te lactose. I whakaatuhia e ā rāua rangahau ka taea e ngā huakita te whakahaere i te whakaaturanga ira i runga i te wātea o te substrate, ā, ko tēnei tikanga e uru ana ki te taunekeneke o ngā pūmua whakahaere me te DNA i ngā wāhi motuhake.
Ngā Wāhanga Matua o Operon
He maha ngā wāhanga nui o tētahi operon:
1. Kaiwhakatairanga
He raupapa DNA te kaiwhakatairanga e herea ai te RNA polymerase hei tīmata i te tuhi. Ka pā te kaha o te kaiwhakatairanga (te ngāwari o te herea o te RNA polymerase) ki te tere o te tuhi.
2. Kaiwhakahaere
Ko te kaiwhakahaere he wāhanga o te DNA e mahi ana hei "pana" nā te mea koinei te wāhi e piri ai ngā pūmua whakahaere, pērā i ngā kaikōpiri. Ina herea te kaikōpiri ki te kaiwhakahaere, ka āraia te tuhi.
3. Ngā ira hanganga
Koinei ngā ira e waehere ana mō ngā pūmua mahi, hei tauira, ngā whākōkī mō te pākia o tētahi matū, ngā pūmua kawe kiriuhi, ngā wāhanga hanga koiora rānei.
4. Ngā ira whakahaere (kei waho tonu i te operon)
Ka whakamāramahia e ngā ira whakahaere ngā pūmua whakahaere pērā i ngā mea aukati, ngā mea whakahohe rānei. Ka taea e ngā hua ira whakahaere te here ki ngā kaiwhakahaere, ki ētahi atu rohe rānei i runga i te DNA hei whakahaere i te tuhi ira.
Haunga ngā wāhanga matua o runga ake nei, kei ētahi operon ngā pae here whakahohe, ngā kaiwhakamutu whakawhiti kupu, me ētahi atu huānga e whakapai ake ana i te mana whakahaere o te whakapuakitanga.
He aha i whai hua ai ngā operon ki ngā huakita?
He maha ngā painga urutau o ngā operon:
– Te whakataurite i te whakapuakitanga: Ka taea te whakapuaki ngātahi i ngā ira e whai wāhi ana ki te ara pākia kotahi, kia kore ai he pūmua e "hua kore noa iho" me te kore he hoa.
– Te whai huatanga o te pūngao: He nui ngā rauemi e hiahiatia ana mō te whakaputa pūmua. Mā ngā operon, ka karohia e ngā huakita te moumou pūngao ina kore ngā āhuatanga taiao e tautoko i te whakamahinga o taua ara.
– Tauhohenga tere: Nā te mea he kotahi te whakahaere o ngā ira, ka taea e ngā panoni iti o te whakahaere (hei tauira, te herea pehi) te whakarerekē i te whakaaturanga o ētahi ira i te wā kotahi.
Ngā Tikanga Whakahaere: Ngā Pūnaha Whakaoho me te Whakaiti
I ngā tikanga tuku iho, ka taea te wehewehe i te whakahaere operon kia rua ngā wāhanga whānui i runga i tōna arorau whakahaere: ngā operon whakaohooho me ngā operon pehi.
1. Ngā Operon Whakaoho: He tauira o te Operon lac
Ko te operon lac i roto i te E. coli te kaiwhakahaere i te pakaru o te lactose. Ko ōna ira hanganga matua ko lacZ, lacY, me te lacA:
– ka whakakōrerohia e te lacZ te β-galactosidase e wawahi ana i te lactose,
– ka whakakōrerohia e te lacY tētahi urunga e āwhina ana ki te whakauru i te lactose ki roto i te pūtau,
– ka whakakōrerohia e lacA te transacetylase (he mahi tāpiri).
I te korenga o te lactose, ka herea te pūmua aukati (te hua o te ira lacI) ki te kaiwhakahaere, ka aukati i te RNA polymerase, ā, ka kore, ka iti rawa rānei te tuhi. Ina wātea te lactose, ka hurihia ētahi o te lactose ki te allolactose (he kaiwhakaoho), ka herea ki te kaiwhakaoho. Ka huri tēnei here i te āhua o te kaiwhakaoho, ka taea ai e ia te wehe atu i te kaiwhakahaere. Nō reira, ka taea e te RNA polymerase te tārua i ngā ira lac, ā, ka tīmata ngā huakita ki te whakaputa i ngā whākōkī wehewehe lactose.
He uaua ake te whakahaere i te operon lac mā te pehi catabolite. Ina wātea te hukahuka (te pūtake pūngao pai), ka heke ngā taumata cAMP, ka ārai i te hanganga pai o te matatini CAP-cAMP. Ki te kore tēnei kaiwhakaoho, ahakoa kei reira te lactose, kāore e tino pai te whakaaturanga operon lac. Nō reira, ka whakatairangahia e ngā huakita te hukahuka i te whakamahinga o te lactose.
2. Ngā Operon Ārai: He tauira o te Operon trp
Ko te operon trp te kaiwhakahaere o te hanga koiora o te waikawa amino tryptophan. He rerekē ki te operon lac, he mahi tonu te operon trp ina iti te tryptophan, nā te mea me hanga e te pūtau ia anō. Ina teitei ngā taumata tryptophan, ka mahi te tryptophan hei korepressor: ka herea ki te trp repressor, ka whakahohe i te kaha o te repressor ki te herea ki te kaiwhakahaere, ā, ka mutu te tuhi.
He māmā noa te arorau: ki te nui te tryptophan, kāore e hiahiatia he pūngao hei hanga; ka whakawetohia te operon.
Ture Tāpiri: Te Whakaiti
I roto i ētahi operon, tae atu ki te operon trp, kei reira tētahi atu tikanga e kiia nei ko te whakaiti. E whakawhirinaki ana tēnei tikanga ki te hononga piripono i waenga i te tuhi me te whakamāori i roto i ngā huakita (ka taea e ngā mea e rua te puta tata i te wā kotahi). I roto i te operon trp, ka taea e te raupapa "kaiārahi" te hanga i tētahi hanganga makawe i runga i te mRNA. Ka taea e tēnei hanganga te mahi hei whakamutu wawe i te tuhi.
Ina teitei te tryptophan, ka tere te neke o te ribosome i tua atu i te rohe kaiārahi, ka taea ai te hanga i te hairpin terminator, ā, ka mutu te tuhi ira i mua i te tuhi katoa o te ira hanganga. Ina iti te tryptophan, ka tū te ribosome i te codon tryptophan, ka ārai i te hanga o te hairpin terminator, ā, ka taea ai te haere tonu o te tuhi ira. Mā tēnei, ka whiwhi te pūtau i te mana whakahaere pai mō te taumata o te wātea o te tryptophan.
Ngā Operon me te Whatunga Whakahaere Ira Whānui
Ahakoa te āhua māmā o te ariā o te operon, he whatunga uaua te whakahaere ira kitakita. He maha ngā operon kāore i te whakahaerehia e te kotahi pehi, engari e ngā kaiwhakahaere maha, tae atu ki ngā kaiwhakaoho, ngā pūoko taiao, me ngā pūnaha wāhanga-rua e uru ana ki ngā kinase pūmua me ngā kaiwhakahaere urupare. Mā ēnei pūnaha ka taea e ngā kitakita te urutau ki te pH, te pāmahana, te pēhanga osmotic, te wātea o te hauota, ngā matū paitini, me ngā tohu mai i ētahi atu moroiti.
Hei tāpiritanga, ka taea e ngā huakita te whakarerekē i te urunga o te DNA mā roto i ngā pūmua here-nucleoid, ā, ka whakamahia ngā RNA iti e pokanoa ana (sRNA) hei aukati, hei whakarei ake rānei i te whakamāoritanga o ngā mRNA ūnga. Ahakoa rā, ko ngā operon tonu te tūāpapa nui mō te whakarite i ngā ira mahi ki roto i tētahi wae whakahaere kotahi.
Te Hiranga o ngā Operon i roto i te Hangarau Koiora me te Hauora
He mea nui te mārama ki ngā operon i roto i te hangarau koiora. He maha ngā pūnaha whakaaturanga ira taiwhanga e whakamahi ana i ngā kaiwhakatairanga me ngā kaiwhakahaere i ahu mai i ngā operon kitakita, pērā i te pūnaha ira-whakaoho hei whakaputa i ngā pūmua recombinant. I roto i te rongoā, he mea nui anō hoki te whakahaere operon ki te mate kitakita—ko ētahi ira kaha me te ātete ki ngā paturopi ka whakahaeretia kia tere te whakahohe ina noho ngā kitakita i roto i te tinana, ina pāngia rānei e te rongoā.
Hei tāpiri atu ki tēnā, mā te ako i ngā operon ka āwhina i ngā kairangahau ki te mārama ki te whanaketanga o ngā huakita mā te whakarōpū i ngā ira e mahi tahi ana. Ko ngā rōpū ira kua whakaritea hei operon ka neke haere i roto i te whakawhiti ira whakapae , ka taea ai e ngā āheinga pākia hou te puta wawe i roto i ngā taupori huakita.
Whakamutunga
He rautaki whakahaere ira ahurei, whai hua hoki ngā operon i roto i ngā huakita, e āhei ai te whakaatu tahi i ngā ira maha i raro i te mana whakahaere kotahi. Mā roto i ngā wāhanga pēnei i ngā kaiwhakatairanga, ngā kaiwhakahaere, ngā ira hanganga, me ngā pūmua whakahaere, ka taea e ngā huakita te urupare tere me te whai hua ki ngā huringa taiao. E whakaatu ana ngā operon lac me trp i ngā arorau whakahaere matua e rua—te whakaoho me te pehi—e whakatikatikaina ana e ngā tikanga tāpiri pēnei i te pehi catabolite me te whakaiti. Mā te mārama ki ngā operon, ehara i te mea ka whakaratohia he māramatanga taketake mō te koiora ngota huakita engari ka whakaratohia hoki he turanga whai hua mō ngā tono hangarau koiora, te rangahau ira, me ngā rautaki mō te rongoā i ngā mate pāwera.
Ki te hiahia koe, ka taea e au te tāpiri i tētahi whakaahua kauwhata o ngā wāhanga operon, he ripanga whakatairite lac vs trp, he rārangi pukapuka me ngā hautaka rānei hei whakapakari i tēnei tuhinga.
