Fosforilacija proteina u biljaka

undergraduate thesis

• Title (english): Plant protein phosphorilation
• Author: Matija Šimac
• Mentor: Biljana Balen (mentor)
• Granter: University of Zagreb; Faculty of Science; (Department of Biology); Zagreb
• Defense date and country: 2010, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Biology

Abstract

Signalizacija u biljaka i fotosinteza su u vrlo bliskom odnosu. Fotosinteza je vrlo važan mehanizam koji nudi asimilate koji su potrebni za rast same biljke, stoga i hranu i vlakna koja podržavaju sav životinjski svijet. Protein-protein interakcije imaju vrlo važnu ulogu u staničnim procesima kao signalnoj transdukciji, regulaciji životnog ciklusa stanice, metaboličkoj regulaciji. Regulacija samih proteinskih interakcija u nekom vremenu i prostoru je vrlo značajna za preživljavanje kako na staničnoj razini tako i cijelog organizma. Reverzibilna fosforilacija specifičnog aminokiselinskog ostatka unutar fosfoprotein-vezujuće domene ciljanog proteina protein kinazama može uzrokovati promjene u konformaciji i naboju. Te promjene mogu dovesti do stvaranja spojnih mjesta za fosfopeptid-vezujuće proteine na ciljanom proteinu. U uvjetima svjetla enzim je u svojoj aktivnijoj defosforiliranoj formi. Nitrat reduktaza je jedan od prvih otkrivenih enzima koji se vežu za proteine 14-3-3. Kasnije je dokazano da su proteini 14-3-3 signalni proteini koji se vežu na fosforilirane serinske i treoninske ostatke i da stupaju u interakciju s raznovrsnim proteinima i u biljkama i u životinjama. Proteini 14-3-3 vežu fosforilirane proteine u pukotinu između podjedinica, vezujući se na jednostavne motive koji uključuju fosforilirane serinske ili treoninske ostatke (pS ili pT). U nekim je slučajevima vezanje proteina iz grupe 14-3-3 za nitrat reduktazu inhibirano (kad je koncentracija kationa vrlo niska), dok u nekim slučajevima kationi nemaju gotovo nikakve uloge na vezanje. Svi kationi utječu na iste proteinske interakcije, što sugerira- kako se koncentracija kationa mijenja, na primjer, kao odgovor na stres, sklonost proteina 14-3-3 za vezanje na različite mete će se također mijenjati. Razina fosforilacije proteina se također mijenja u odgovoru na prisutnost ROS-a. Oni se proizvode u mnogim staničnim dijelovima, kao odgovor na hormone koji reguliraju normalni biljni rast i razvoj, kao i na razne abiotičke i biotičke stresove. Metioninski ostatak je vrlo hidrofoban u reduciranom obliku. Blagom oksidacijom reverzibilno prelazi u mnogo polarniji sulfoksid (MetSO). Ova modifikacija se popravlja peptid metionin sulfoksid reduktaza, ali biljne i životinjske stanice u normalnom stanju će uvijek imati nekoliko ostataka MetSO. Jača oksidacija rezultira ireverzibilnim prijelazom sulfoksida u sulfon (MetO2) koji se može popraviti jedino degradacijom proteina. Moguće je da se ta sklonost da se metioninski ostatci oksidiraju koristi za signalizaciju ROS-a.

Abstract (english)

Signaling in plants and photosynthesis are in a very close relationship. Photosynthesis is a very important mechanism that offers asimilates required for plant growth and growth for all other organisms depending on plants. Protein-protein interactions play a very important role in cellular processes such as signal transduction, regulation of the life cycle of cells, metabolic regulation. Therefore, regulation of protein interactions at a specific time and space is very important for the survival on the cellular level and for an organism. Reversible phosphorylation of specific amino acid residue within the phosphoprotein-binding domain of protein kinase target protein, can cause changes in conformation and charge. These changes may lead to the formation of docking places for fosfopeptid-binding proteins on the target protein. In light conditions the enzyme is in its active dephosphorylated form. Nitrate reductase is one of the first enzymes discovered that bind to 14-3-3 proteins. Later it was proved that 14-3-3 proteins are signaling proteins that bind to serin and threonin. Phosphorylated serine residues interact with various proteins (known as client proteins) in plants and animals. 14-3-3 proteins bind phosphorylated proteins in a cleft between the subunits, binding to simple motifs that include phosphorylated threonin or serine residues (pS or pT). In some cases, the binding of 14-3-3 with nitrate reductase was inhibited, as in some cases cations have almost no role in binding. All cations affect the same protein interactions, which suggest that changes in cation conentation, (such as stress response), will change the tendency of 14-3-3 protein binding to different targets. The level of protein phosphorylation also changes in response to ROS. They are produced in many parts of the cell as response to hormones that regulate normal plant growth and development as well as a variety of abiotic and biotic stresses. Methionine residue is very hydrophobic in reduced form. Mild reversible oxidation produces a much more polar sulfoxide (MetSO). This modification repairs peptide methionine sulfoxide reductase, but plant and animal cells in basal metabolism will always have a few residue of the MetSO. Stronger oxidation results in an irreversible conversion into the sulfone (MetO2 ) that can only be repaired by protein degradation. It is possible that this propensity for methionine residues to oxidize may be exploited in response to signalling by ROS.

• Keywords: fosforilacija proteina; biljke
• Keywords (english): plant protein phosphorilation
• Language: croatian
• URN:NBN: urn:nbn:hr:217:516310
• Study programme: Title: Molecular Biology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) molekularne biologije (sveučilišni/a prvostupnik/prvostupnica (baccalaureus/baccalaurea) molekularne biologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2018-04-04 09:25:43