Chloroplasts ntawm algae thiab nroj tsuag yog lub cellular engine uas hloov hnub ci zog rau hauv tshuaj zog los ntawm photosynthesis. Cov organelles no, bounded los ntawm ib lub hnab ntawv nrog ob daim nyias nyias, muaj lawv tus kheej genome uas nws qhia yog nruj nreem sib koom tes nrog hais tias ntawm lub nuclear genome. Feem ntau ntawm chloroplast proteins yog encoded los ntawm cov noob caj noob ces, txhais nyob rau hauv lub cytosol raws li precursor proteins uas muaj ib tug sib lawv liag ntawm lawv cov amino terminus uas ua hauj lwm raws li daim pib nkag mus rau hauv chloroplasts.
Protein ntshuam mus rau hauv chloroplasts yog kho los ntawm ob lub membrane protein complexes hu ua TOC thiab TIC nyob rau hauv lub sab nrauv thiab sab hauv lub hnab ntawv membrane, feem. Cov complexes no ua lub luag haujlwm tseem ceeb hauv tshuaj chloroplast biogenesis, nyob rau hauv sib dhos ntawm photosynthetic apparatuses thiab nyob rau hauv ntau yam metabolic txoj kev. Qhov sib txawv ntawm cov protein subunits ntawm TOC thiab TIC tau raug txheeb xyuas thiab tus yam ntxwv, thiab TOC thiab TIC tau tshwm sim los ua ib qho supercomplex ua ke. Txawm li cas los xij, qhov sib txawv ntawm cov proteins ntawm TOC thiab TIC sib sau ua ke los tsim cov channel rau kev hloov pauv cov protein hla lub hnab ntawv chloroplast tsis meej, thiab txoj hauv kev hloov pauv cov protein hauv TOC thiab TIC tseem tsis pom.
Hauv kev tshawb fawb luam tawm hauv online hauv xwm, Liu Zhenfeng pawg ntawm lub koom haum ntawm Biophysics ntawm Suav Academy ntawm Sciences, koom tes nrog Prof. Jean-David Rochaix los ntawm University of Geneva, Switzerland, tau muab cov kev xav ntev-awaited rau hauv cov molecular Cheebtsam, peb-dimensional lub koom haum thiab muaj peev xwm protein. Translocation txoj kev ntawm TOC-TIC supercomplex los ntawm ib leeg-celled ntsuab alga npe hu ua Chlamydomonas reinhardtii.
Cov kws tshawb fawb tau piav qhia cov qauv supramolecular ntawm TOC-TIC supercomplex los ntawm cryo-electron microscopy.
Kaum peb cov protein sib txawv subunits hauv no supercomplex tau pom. Nrog rau kev zam ntawm Tic214 encoded los ntawm chloroplast genome, tag nrho lwm cov subunits yog nuclear encoded. Lawv tau sib sau ua ke rau hauv TOC complex nyob rau hauv lub txheej membrane, lub interemembrane chaw complex (ISC) thiab lub TIC complex nyob rau hauv lub puab membrane. Remarkably, nws tau pom tias qhov loj tshaj plaws membrane protein Tic214 spans lub puab daim nyias nyias, qhov chaw intermembrane thiab cov txheej membrane, txuas rau lwm yam. protein subunits zoo li tus choj thiab feem ntau yuav kuj ua raws li ib tug scaffold.
TOC complex nyob rau hauv daim nyias nyias yog tsim los ntawm Toc34, Toc90 thiab Toc75, flanked ntawm Toc90 sab los ntawm lub Ctap4-Ctap3 complex. Ib tug hybrid chim-puab channel yog tsim los ntawm Toc90 thiab Toc75 ntawm lub sab nrauv membrane. Cov channel muaj qhov nkag ntawm cytosolic sab thiab ob qhov kev tawm qhib mus rau qhov chaw nruab nrab, nrog rau lub rooj vag sab nraud ntawm lub qhov rooj. lipid daim tawv nqaij. Ib qho phytic acid (tseem hu ua inositol hexaphosphate / InsP6) molecule intercalates ntawm qhov sib cuam tshuam ntawm Toc90 thiab Tic214, stabilizing lawv lub rooj sib txoos zoo li lub npoo.
Lub intermembrane-chaw domain ntawm Tic214, Tic100, Tic56, Ctap3 thiab Ctap5 intertwine nrog ib leeg los tsim ib tug pej thuam zoo li qauv txuas TOC nrog TIC. Hauv sab hauv daim nyias nyias, lub membrane-embedded domains ntawm Tic214, Tic20, Ctap5 thiab peb subunits me me (lub npe Simp1, Simp2 thiab Simp3) tsim TIC complex. Plaub lipid molecules ua haujlwm kom ruaj khov ntawm kev sib dhos ntawm cov channel zoo li funnel nyob rau ntawm qhov sib cuam tshuam ntawm Tic214 thiab Tic20 thiab tiv thaiv cov channel los ntawm kev xau.
Raws li cov ntaub ntawv tsim qauv, cov kws tshawb fawb tau txheeb xyuas cov yam ntxwv ntawm cov pores hauv TOC thiab TIC raws. Lawv tuaj yeem kwv yees qhov kev sib cuam tshuam ntawm kev hloov pauv peptide thiab TIC complex los ntawm kev simulation molecular dynamics.
Kev txhawb nqa los ntawm kev soj ntsuam ntawm ob txoj kab pores txuas los ntawm qhov zawj ntawm qhov chaw thiab cov ntaub ntawv biochemical thiab kev ua haujlwm dhau los, ntau txoj hauv kev tau thov kom suav nrog kev hloov pauv ntawm cov khoom sib txawv ntawm cov preproteins los ntawm TOC-TIC supercomplex kom sib txawv hauv zos chloroplast compartments.