Isakhiwo kanye Nomsebenzi We-Ribosomes
Ama-ribosome ayizingxenye ezibalulekile zawo wonke amangqamuzana aphilayo, asebenza njengezikhungo zokwenziwa kwamaprotheni, okubalulekile ekukhuleni nasekusebenzeni kwamaseli. Isakhiwo esiyinkimbinkimbi kanye nemisebenzi eningiliziwe yama-ribosome kube yinto ebalulekile ocwaningweni lwesayensi amashumi eminyaka, enikeza ukuqonda okujulile ngezindlela eziyisisekelo zama-molecule zokuphila. Lesi sihloko sizoxoxa ngokuningiliziwe ngesakhiwo kanye nomsebenzi wama-ribosome, kanye nokubaluleka kwawo kwebhayoloji kanye nokuqonda kwamanje emkhakheni we-biology yama-molecule.
Isakhiwo se-Ribosome
Ama-Ribosome ayizinhlanganisela ze-ribonucleoprotein ezakhiwe yi-ribosomal RNA (rRNA) kanye namaprotheni e-ribosomal. Ngokuvamile, ama-ribosome ahlukaniswe ngama-subunit amabili: i-subunit enkulu kanye ne-subunit encane. Ezintweni eziphilayo ze-prokaryotic ezifana namabhaktheriya, ama-ribosome angama-70S, ahlukaniswe abe yi-subunit encane engama-30S kanye ne-subunit enkulu engama-50S. Ezintweni eziphilayo ze-eukaryotic, njengezilwane nezitshalo, ama-ribosome angama-80S, aqukethe i-subunit encane engama-40S kanye ne-subunit enkulu engama-60S. Kufanele kuqashelwe ukuthi i-"S" ibhekisela kumayunithi e-Svedberg, okuyiyunithi yokusatshalaliswa esetshenziselwa ukulinganisa usayizi wezinhlayiya ekugxilweni.
Iyunithi Encane
I-subunit encane ye-ribosome idlala indima ekufundeni i-mRNA (i-messenger RNA) ukuze ihunyushwe ibe yiprotheni. Kuma-ribosome e-prokaryotic, i-subunit encane ye-30S iqukethe i-rRNA engu-16S kanye namaprotheni e-ribosomal angaba ngu-21. Kuma-ribosome e-eukaryotic, i-subunit encane ye-40S iqukethe i-rRNA engu-18S kanye namaprotheni e-ribosomal angaba ngu-33. I-rRNA ku-subunit encane idlala indima ebalulekile ekuqaphelweni nasekubopheni i-mRNA kanye nasekufaniseni i-tRNA (ukudlulisa i-RNA) nama-codon afanele ku-mRNA ngesikhathi sokuhumusha.
I-Subunit Enkulu
I-subunit enkulu ye-ribosome yilapho kwenzeka khona ukwakheka kwe-peptide bond phakathi kwama-amino acid, inqubo ebalulekile ekunwetshweni kwe-polypeptide chain. Kuma-ribosome e-prokaryotic, i-subunit enkulu ye-50S iqukethe i-23S rRNA, i-5S rRNA, kanye namaprotheni e-ribosomal angaba ngu-34. Ngokuphambene nalokho, kuma-ribosome e-eukaryotic, i-subunit enkulu ye-60S iqukethe i-28S rRNA, i-5.8S rRNA, i-5S rRNA, kanye namaprotheni e-ribosomal angaba ngu-49. Ama-Ribozyme, izingxenye ze-RNA ezikwazi ukuvuselela ukusabela kwamakhemikhali, zitholakala ku-subunit enkulu futhi zidlala indima ebalulekile ekuqalisweni kwe-prototypical kokwakheka kwe-peptide bond.
Umsebenzi wamaRibosome
Ukuhumusha Amaprotheni
Umsebenzi oyinhloko wama-ribosome ukulawula ukuhumusha amaprotheni, inqubo lapho ama-ribosome ehumusha khona ulwazi lwezakhi zofuzo olufakwe ku-mRNA lube ngamaketanga e-polypeptide azogoqwa abe amaprotheni asebenzayo. Inqubo yokuhumusha ingahlukaniswa ngezigaba ezintathu eziyinhloko: ukuqaliswa, ukunwetshwa, kanye nokuphela.
1. Ukuqaliswa: Le nqubo iqala lapho i-subunit encane ye-ribosome ibopha ku-mRNA eduze kwe-codon yayo yokuqala. Izinto zokuqaliswa kanye nama-tRNA okuqala aphethe ama-amino acid i-methionine (kuma-eukaryotes) noma i-formylmethionine (kuma-prokaryotes) adlala indima ebalulekile kule nqubo. Le nhlanganisela ibe isihlangana ne-subunit enkulu ukwakha i-ribosome esebenzayo.
2. Ukwelulwa: Kulesi sigaba, i-ribosome iqala ukuhamba eduze kwe-mRNA, ifunda i-codon ngayinye futhi ilethe i-tRNA efanele equkethe i-amino acid efanele. Yilapho i-peptidyl transferase, i-enzyme eyingxenye ye-subunit enkulu ye-ribozyme, ikhuthaza ukwakheka kwezibopho ze-peptide phakathi kwama-amino acid, yandise uchungechunge lwe-polypeptide.
3. Ukuphela: Lapho i-ribosome ifinyelela ku-codon yokuphela ku-mRNA, izici zokuphela ziyayibona le codon futhi zenze kube lula ukukhululwa kochungechunge lwe-polypeptide oluqediwe kanye nokuhlukaniswa kwe-ribosome ku-mRNA.
Ukulawulwa Kokwenziwa Kwamaprotheni
Ama-Ribosome nawo ahilelekile ekulawuleni ukwakheka kwamaprotheni, esebenza namanye amaprotheni ahlukahlukene kanye nama-RNA ukuqinisekisa ukuthi amaprotheni afanele akhiqizwa ngamanani adingekayo ngesikhathi esifanele. Lo mthetho ubalulekile ekugcineni i-homeostasis yamaseli kanye nokusabela ezinguqukweni zemvelo.
I-Inspeksi Kualitas
Ama-Ribosome anezindlela ezakhelwe ngaphakathi zokuqinisekisa ikhwalithi yamaprotheni akhiqizwayo. Lokhu kufaka phakathi izindlela ezithola amaphutha ku-tRNA noma i-mRNA futhi zivimbele ukunwebeka noma zibangele ukuwohloka kwama-molecule angalungile. Le nqubo ibalulekile ukuqinisekisa ukuthi kukhiqizwa amaprotheni asebenzayo kuphela, okunciphisa ingozi yokulimala kwamangqamuzana noma ukufa kwamangqamuzana.
Ukubaluleka Kwezinto Eziphilayo kanye Nezicelo
Ukuqonda isakhiwo kanye nomsebenzi wama-ribosome akubalulekile nje kuphela kwisayensi eyisisekelo kodwa futhi kunezindlela eziningi ezisebenzayo kwezokwelapha kanye ne-biotechnology. Isibonelo, ama-antibiotic amaningi asebenza ngokugxila kuma-ribosome e-prokaryotic, evimbela ukwakheka kwamaprotheni ebhaktheriya ngaphandle kokuthinta ama-ribosome e-eukaryotic. Ucwaningo oluqhubekayo ngama-ribosome luthembisa nokuthuthukisa izindlela ezintsha zokwelapha izifo ezahlukahlukene.
Ukutholwa Kwakamuva
Ucwaningo lwakamuva olusebenzisa amasu athuthukile njenge-X-ray crystallography kanye ne-cryo-electron microscopy (Cryo-EM) lunikeze isithombe esiningiliziwe sesakhiwo se-ribosome. Lokhu okutholiwe kwembule ukwakheka okuguquguqukayo kwe-ribosome ngesikhathi sokuhumusha, ukuhambisana kwezingxenye ze-ribosome, kanye nokusebenzisana kwayo nezinye izici zokuhumusha. Lolu lwazi olusha alugcini nje ngokujulisa ukuqonda kwethu izindlela eziyisisekelo ze-ribosome kodwa futhi luvula izindlela ezintsha zocwaningo lwezokwelapha kanye nokuthuthukiswa kwemithi.
Isiphetho
Ama-Ribosome ayimishini yama-molecule eyinkimbinkimbi futhi ebalulekile ephethe ukuhumusha ulwazi lwezakhi zofuzo lube amaprotheni asebenzayo. Ngesakhiwo sawo esiyinkimbinkimbi sama-subunit amabili kanye nokusebenzisana okunembile phakathi kwamaprotheni e-rRNA kanye ne-ribosomal, ama-ribosome angenza ukwakheka kwamaprotheni ngempumelelo ephezulu. Ukuqonda okujulile kwesakhiwo nomsebenzi we-ribosome kuyaqhubeka nokukhula, okuqhuba ucwaningo olwengeziwe ku-biology yama-molecule kanye nezicelo ezibalulekile zezokwelapha. Ukutholwa kwamuva nje kulo mkhakha kwenze ama-ribosome aba yinto ebalulekile ekufundweni kokuphila ezingeni lama-molecule.
