Ntchito ya Amino Acids mu Kapangidwe ka Mapuloteni
Mapuloteni ndi amodzi mwa ma biomolecule akuluakulu omwe amapanga zamoyo. Pafupifupi njira zonse zamoyo—kuyambira kupangika kwa minofu ndi ntchito ya ma enzyme mpaka kunyamula zinthu ndi mayankho a chitetezo chamthupi—zimadalira mapuloteni. Komabe, mapuloteni si amodzi okha, okonzeka kupangidwa. Mapuloteni amapangidwa ndi zigawo zazing'ono zotchedwa amino acid. Kumvetsetsa ntchito ya amino acid mu kapangidwe ka mapuloteni kumatanthauza kumvetsetsa momwe mapuloteni amapezera mawonekedwe enaake, kukhazikika, komanso kuthekera kochita ntchito zapadera kwambiri zamoyo.
Ma amino acid monga "zomangira" mapuloteni
Ma amino acid ndi mamolekyu achilengedwe omwe nthawi zambiri amakhala ndi magulu awiri ofunikira: gulu la amino (-NH₂) ndi gulu la carboxyl (-COOH), ndi atomu yapakati ya kaboni (alpha carbon) yolumikizidwa ku gulu la mbali (R). Gulu la R ili ndi lomwe limasiyanitsa amino acid imodzi ndi inzake. Pali ma amino acid 20 omwe maselo amagwiritsa ntchito popanga mapuloteni.
Ntchito yaikulu kwambiri ya amino acid ndi monga ma monomers omwe amalumikizana pamodzi kuti apange ma polima, omwe ndi mapuloteni. Mgwirizano womwe umalumikiza ma amino acid umatchedwa peptide bond, womwe umapangidwa kudzera mu condensation reaction (kutulutsidwa kwa molekyulu yamadzi) pakati pa gulu la carboxyl la amino acid imodzi ndi gulu la amino la amino acid ina. Unyolo uwu wa ma amino acid umapanga unyolo wa polypeptide, womwe umapinda kukhala kapangidwe ka mapuloteni ogwira ntchito.
Mndandanda wa amino acid umatsimikiza kapangidwe ndi ntchito yake.
Mu mapuloteni, ndondomeko ya amino acid (yomwe imatchedwa kapangidwe kake koyamba) si mndandanda wa zigawo zokha, koma ndi "code" yomwe imatsimikiza momwe puloteniyo idzapindikira, kukhazikika kwake, ndi ntchito yake. Ndondomekoyi imayendetsedwa ndi chidziwitso cha majini (DNA) kudzera mu njira zolembera ndi kumasulira.
Kusintha pang'ono kwa ndondomekoyi kungakhale ndi zotsatirapo zazikulu. Mwachitsanzo, kusintha amino acid imodzi kungasinthe mawonekedwe a puloteni, kuchepetsa magwiridwe ake kapena kuipangitsa kukhala yoopsa. Izi zikutanthauza kuti amino acid sizinthu zokha zomangira komanso zimadziwitsanso umunthu wa puloteniyo. Kapangidwe kake koyamba ndi komwe kamapanga maziko a mapangidwe a mapangidwe apamwamba.
Udindo wa amino acid mu kapangidwe kachiwiri: α-helix ndi β-sheet
Unyolo wa polypeptide ukapangidwa, umayamba kupanga mapangidwe opindika am'deralo otchedwa ma secondary structures. Mitundu iwiri yodziwika kwambiri ndi iyi:
1. α-helix (alpha helix): Unyolo wa polypeptide umazungulira ngati kasupe.
2. β-sheet (beta sheet): Maunyolo a polypeptide amakonzedwa motsatizana kuti apange pepala lopindidwa.
Kapangidwe kachiwiri kamakhazikika makamaka ndi ma hydrogen bond pakati pa maatomu omwe ali mu msana wa polypeptide, osati ndi magulu a R. Komabe, magulu a R amakhudza kwambiri chizolowezi cha α-helices kapena β-sheets kupanga. Mwachitsanzo, proline nthawi zambiri "imaswa" ma helices chifukwa cha kuuma kwake, pomwe alanine nthawi zambiri imakonda kupangika kwa helix.
Motero, ma amino acid amagwira ntchito ngati owongolera mapindidwe am'deralo kudzera mu mawonekedwe awo a mankhwala ndi mawonekedwe a magulu awo am'mbali.
Kapangidwe kapamwamba: Kupindika kwa 3D kumatsimikiziridwa ndi kuyanjana kwa gulu la R.
Kapangidwe kapamwamba ndi mawonekedwe onse a unyolo wa polypeptide. Pa siteji iyi, ntchito ya amino acid imamveka bwino, pamene kuyanjana pakati pa magulu a R kumatsimikiza momwe puloteni "imatsekereza" mawonekedwe ake. Kuyanjana kofunikira komwe kumakhudzidwa ndi mtundu wa amino acid ndi:
– Kuyanjana kwa hydrophobic: Ma amino acid omwe si a polar (monga valine, leucine, isoleucine) nthawi zambiri amasonkhana mkati mwa mapuloteni kuti apewe madzi. Ichi ndi chimodzi mwa zinthu zazikulu zomwe zimapangitsa kuti mapuloteni apindike.
– Ma hydrogen bonds: Ma amino acid a polar (monga serine, threonine, asparagine, glutamine) amatha kupanga ma hydrogen bonds omwe amathandiza kukhazikika kwa mapindidwe.
– Ma Ionic bonds (milatho yamchere): Ma amino acid odzaza (ma acid: aspartate, glutamate; maziko: lysine, arginine, histidine) amatha kukokana kuti apange milatho yamchere yomwe imalimbitsa kapangidwe kake.
– Mphamvu za Van der Waals: Ngakhale kuti ndi zofooka, kuyanjana kumeneku kumakhala kofunikira pamene zambiri zimachitika nthawi imodzi m'mapuloteni omangidwa bwino.
– Ma bond a Disulfide: Ma residues awiri a cysteine akhoza kupanga ma covalent disulfide (S-S) bond, omwe ndi olimba kwambiri ndipo amachita gawo lalikulu pakukhazikika kwa mapuloteni, makamaka mapuloteni akunja monga keratin kapena ma antibodies.
Apa tikuona kuti ma amino acid samangopanga mapuloteni okha, komanso amapanga "maukonde ogwirizana" omwe amatsimikiza mphamvu, kusinthasintha, ndi kukhazikika kwa mapuloteni.
Kapangidwe ka Quaternary: amino acids amapanga mgwirizano wa ma subunits angapo
Mapuloteni ena sagwira ntchito ngati unyolo umodzi, koma monga kuphatikiza kwa maunyolo angapo a polypeptide otchedwa ma subunits. Kapangidwe ka ma subunits aka kamatchedwa kapangidwe ka quaternary. Chitsanzo chodziwika bwino ndi hemoglobin, yomwe imakhala ndi ma subunits anayi.
Ma amino acid amathandizira kapangidwe ka quaternary kudzera mu kuyanjana pakati pa malo a subunit: kuyanjana kwa hydrophobic, ma hydrogen bonds, ndi ma ionic bonds. Kapangidwe ka amino acid pa subunit interface kamatsimikizira momwe ma subunit amamangirirana mwamphamvu, momwe puloteni imasinthira mosavuta, komanso momwe imagwirira ntchito mogwirizana. Mwanjira ina, ma amino acid amagwira ntchito ngati "maloko" omwe amagwirira magawo osiyanasiyana a puloteni pamodzi kotero kuti amagwira ntchito ngati unit.
Ma amino acid amapanga malo ogwirira ntchito ndipo amatsimikizira kudziwika kwa puloteni.
Ntchito ya mapuloteni imadalira kwambiri mawonekedwe awo ndi kapangidwe kake ka pamwamba. Ma amino acid amapanga zinthu zofunika kwambiri monga:
– Malo ogwirira ntchito a enzyme, komwe kumachitika mankhwala.
– Malo omangira minofu ya m'mitsempha, mwachitsanzo komwe mahomoni, ma ayoni, kapena mamolekyu ang'onoang'ono amamangirira.
- Malo ozindikira, mwachitsanzo mu ma antibodies kapena ma membrane receptors.
Kupadera kwa magulu a R kumalola mapuloteni kukhala ndi malo ozungulira oyenera ntchito zinazake. Mwachitsanzo, histidine nthawi zambiri imagwira ntchito mu catalysis ya enzyme chifukwa imatha kulandira kapena kumasula ma proton pa pH ya thupi . Serine imatha kugwira ntchito ngati nucleophile mu serine proteases. Cysteine imatha kupanga ma covalent bonds osakhalitsa mu ma enzyme enaake. Kuphatikiza kwa ma amino acid angapo mu mawonekedwe enaake kumapanga malo ogwirira ntchito enieni.
Ma amino acid amakhudza kukhazikika kwa mapuloteni ku pH ndi kutentha.
Mikhalidwe yachilengedwe monga pH, kutentha, ndi kuchuluka kwa mchere ingakhudze mapuloteni. Ma amino acid omwe ali ndi mphamvu amakhudzidwa kwambiri ndi kusintha kwa pH chifukwa kuchuluka kwa ionization yawo kumasintha. Pamene pH isintha, ma ionic bond amatha kufooka kapena kulimba, zomwe zimapangitsa kusintha kwa kapangidwe ka tertiary kapena quaternary. Ichi ndi chimodzi mwa zifukwa zomwe mapuloteni amatha kusokonekera (kutaya mawonekedwe ndi ntchito yawo) pansi pa mikhalidwe yovuta kwambiri.
Kuphatikiza apo, kapangidwe ka amino acid kamatsimikiziranso kukana kutentha. Mapuloteni omwe amakhala okhazikika kutentha kwambiri (mwachitsanzo, m'zamoyo zokonda kutentha) nthawi zambiri amakhala ndi ma ionic ambiri komanso kapangidwe kolimba. Chifukwa chake, kusankha mtundu wa amino acid ndi malo ake mu puloteni kumathandizira mwachindunji kukana mapuloteni.
Kusintha pambuyo pa kumasulira: amino acid monga mfundo "zomaliza" za mapuloteni
Puloteni ikapangidwa, zotsalira zina za amino acid zimatha kusinthidwa pambuyo pa kusinthidwa, monga phosphorylation, methylation, acetylation, kapena glycosylation. Kusintha kumeneku kumachitika nthawi zambiri pa amino acids enaake: serine/threonine/tyrosine ya phosphorylation, lysine ya acetylation, kapena asparagine ya glycosylation. Cholinga chawo ndikuwongolera momwe mapuloteni amagwirira ntchito, malo mkati mwa selo, kapena momwe amagwirira ntchito ndi mapuloteni ena.
Izi zikusonyeza kuti ntchito ya amino acid siimaima pakupanga mapangidwe oyambira, komanso imakhala malo owongolera zamoyo kuti zizitha kuyendetsa bwino ntchito ya mapuloteni.
Mapeto
Ma amino acids amagwira ntchito yofunika kwambiri pa kapangidwe ka mapuloteni: monga zomangira unyolo wa polypeptide, monga zinthu zomwe zimapangitsa kuti ma protein azitha kupindika, monga zinthu zomwe zimapangitsa kuti ma bond-form akhazikike, ma secondary, tertiary, ndi quaternary, komanso monga omanga malo omwe amagwira ntchito omwe amatsimikiza momwe mapuloteni amagwirira ntchito. Kapangidwe ka mankhwala ka gulu la R—kaya kosakhala polar, polar, charged, kapena kokhoza kupanga ma disulfide bonds—kumapatsa puloteni iliyonse mawonekedwe ake apadera komanso mphamvu zake. Kumvetsetsa ntchito ya ma amino acid mu kapangidwe ka mapuloteni kungatithandize kumvetsetsa chifukwa chake mapuloteni ndi osiyanasiyana komanso ofunikira pamoyo, zomwe zimapanga njira yogwiritsira ntchito kwambiri monga protein engineering, mankhwala, komanso matenda okhudzana ndi majini.
