Qhov sib txawv tseem ceeb ntawm helix-loop-helix thiab helix-tig-helix yog tias helix-loop-helix mediates protein dimerization thaum helix-tig-helix tswj cov noob qhia los ntawm DNA khi.
Ib qho protein motif yog ib qho kev txuag luv luv uas cuam tshuam nrog cov haujlwm sib txawv ntawm DNA. Nws yog feem ntau txuam nrog ib qho chaw tshwj xeeb nrog cov tshuaj lom neeg lossis cov khoom siv lom neeg. Cov motifs no muaj cov cheeb tsam me me ntawm cov qauv peb-dimensional ntawm cov amino acids nrog ntau cov protein molecules. Feem ntau, tus kheej motifs tsuas muaj ob peb yam. Helix-loop-helix thiab helix-tig-helix muaj peb yam. Lawv cov qauv tsim cov qauv tsim muaj xws li cov voj voog uas muaj qhov sib txawv ntawm qhov ntev thiab cov qauv tsis raug.
Helix-Loop-Helix yog dab tsi?
A helix-loop-helix (HLH) yog cov qauv tsim cov qauv protein uas txhais tau tias yog ib tsev neeg loj tshaj plaws ntawm cov khoom siv dimerizing transcription. Cov kev hloov pauv no muaj cov seem ntawm cov amino acids los pab txhawb DNA kev sib khi mechanism, thiab lawv yog dimeric. Protein structural motif muaj ob α-helices, thiab lawv txuas nrog lub voj. Ib lub helix zoo li me me los ntawm ob lub helices, thiab qhov yooj ntawm lub voj tso cai rau dimerization los ntawm kev ntim thiab folding tawm tsam lwm lub helix. Lub helix uas zoo nkaus li loj dua feem ntau muaj cov cheeb tsam DNA-binding. HLH proteins khi rau qhov kev pom zoo ib ntus uas hu ua E-box. Qhov kev pom zoo ua ntu zus yog ib qho kev txiav txim uas suav nrog nucleotide lossis amino acid residues. E-lub thawv yog lub ntsiab lus teb rau DNA hauv qee cov eukaryotes uas ua raws li qhov chaw sib txuas nrog cov protein thiab tswj cov noob qhia.
Daim duab 01: Helix-loop-helix motif
Lub HLH cov ntaub ntawv hloov pauv yog qhov tseem ceeb rau kev txhim kho thiab kev ua haujlwm ntawm tes. HLH cov proteins feem ntau yog nyob rau ntawm 6 pawg, uas tau qhia los ntawm cov ntawv A txog F. Cov ntaub ntawv hloov pauv suav nrog hauv txhua pab pawg yog:
Group A: MyoD, Myf5, Beta2/NeuroD1, Scl, p-CaMK, NeuroD, thiab Neurogenins, group B: MAX, C-Myc, N-Myc, and TCF4
Group C: AhR, BMAL-1-CLOCK, HIF, NPAS1, NPAS3, and MOP5
Pab D; EMC
Group E: HEY1 and HEY2
Group F: EBF1
Vim tias feem ntau cov ntsiab lus ntawm HLH yog heterodimeric, dimerization feem ntau tswj lawv.
Helix-Turn-Helix yog dab tsi?
Helix-tig-helix (HTH) yog cov qauv tsim muaj protein ntau uas muaj peev xwm los khi DNA. Txhua monomer yog koom nrog ob α-helices thiab koom nrog luv luv amino acid strand. Qhov no khi rau ib qho zawj hauv DNA helix. HTH motifs feem ntau tswj cov noob qhia. Kev lees paub HTH thiab khi rau DNA yog ua los ntawm ob lub α-helices. Ib lub helix nyob ntawm N-terminal kawg thaum lwm qhov yog ntawm C-terminus. Hauv ntau qhov xwm txheej, lub helix ua tiav qhov kev lees paub ntawm DNA. Yog li ntawd, nws yog lub npe hu ua lub recognition helix. Kev khi rau qhov zawj hauv DNA tshwm sim los ntawm kev sib cuam tshuam ntawm Van der Waals thiab hydrogen bonds nrog cov hauv paus nthuav tawm. Lwm qhov α-helix stabilizes cov protein thiab DNA sib cuam tshuam thiab tsis ua lub luag haujlwm tseem ceeb hauv kev lees paub. Txawm li cas los xij, qhov kev lees paub helix thiab qhov seem helix muaj qhov taw qhia zoo sib xws.
Daim duab 02: Helix-tig-helix ntawm TetR tsev neeg
HTH yog cais raws li cov qauv thiab kev npaj ntawm cov helices. Cov hom tseem ceeb yog di-helical, tri-helical, tetra-helical, thiab tis HTH. Di-helical hom yog hom yooj yim tshaj plaws nrog ob lub helices thiab ib qho kev ywj pheej folding protein domain. Tri-helical hom muaj nyob rau hauv transcriptional activator Myb. Tetra-helical hom muaj C-terminal helix ntxiv. Thaum kawg, tis HTH yog tsim los ntawm 3- helical pob thiab 3- lossis 4- strand beta daim ntawv.
Dab tsi zoo sib xws ntawm Helix-Loop-Helix thiab Helix-Tig-Helix?
- Helix-loop-helix thiab helix-tig-helix yog protein ntau motifs.
- Ob leeg muaj tus lej feem ntau hauv basal thiab cov ntsiab lus tshwj xeeb.
- Lawv muaj nyob hauv eukaryotes.
Qhov txawv ntawm Helix-Loop-Helix thiab Helix-Tig-Helix yog dab tsi?
Helix-loop-helix mediates protein dimerization, whereas helix-tig-helix tswj cov noob qhia los ntawm DNA khi. Yog li, qhov no yog qhov sib txawv tseem ceeb ntawm helix-loop-helix thiab helix-tig-helix. Tsis tas li ntawd, HLH muaj qee yam proto-oncogenes thiab cov noob muaj feem cuam tshuam nrog kev sib txawv ntawm kev hloov pauv hloov pauv thaum HTH muaj ntau cov noob caj noob ces uas code rau kev hloov pauv. Ntxiv mus, helix-loop-helix feem ntau muaj alpha-helices koom los ntawm lub voj, thaum helix-tig-helix feem ntau muaj cov loops koom los ntawm luv luv amino acid sawv ntsug ua ib zawj.
Cov hauv qab no qhia txog qhov sib txawv ntawm helix-loop-helix thiab helix-tig-helix hauv daim ntawv tabular rau ib sab sib piv.
Summary – Helix-Loop-Helix vs Helix-Turn-Helix
Ib qho protein motif yog ib qho kev txuag luv luv uas cuam tshuam nrog cov haujlwm sib txawv ntawm DNA. Helix-loop-helix thiab helix-tig-helix yog ob hom protein motifs. Qhov sib txawv tseem ceeb ntawm helix-loop-helix thiab helix-tig-helix yog tias helix-loop-helix mediates protein dimerization, thaum helix-tig-helix tswj cov noob qhia los ntawm DNA khi. HLH yog cov qauv tsim cov qauv protein uas txhais tau hais tias yog ib tsev neeg loj tshaj plaws ntawm kev hloov pauv hloov pauv. Protein structural motif muaj ob α-helices, thiab lawv txuas nrog lub voj. HTH yog cov qauv tsim muaj protein ntau uas muaj peev xwm los khi DNA. Txhua monomer yog koom nrog ob α-helices, thiab koom nrog luv luv amino acid strand thiab khi rau ib qho zawj hauv DNA helix. Yog li, qhov no qhia txog qhov sib txawv ntawm helix-loop-helix thiab helix-tig-helix.
