Pi heliks
Pi heliks (π-heliks) je tip sekundarne strukture proteina.[1] π-heliksi su prisutni u oko 15% poznatih struktura. Smatra se da su evoluciona adaptacija formirana umetanjem jedne aminokiseline u α-heliks.[2] Pošto su takva umetanja veoma destabilišuća,[3] do formiranja π-heliksa obično ne dolazi, osim ako to pruža funkcionalnu prednost proteinu. π-heliksi su stoga tipično prisutni u blizini funkcionalnih mesta proteina.[2][4][5]
- ↑ Pauling L, Corey RB, Branson HR (1951). „The Structure of Proteins: Two Hydrogen-Bonded Helical Configurations of the Polypeptide Chain”. Proc. Nat. Acad. Sci. Wash. 37 (4): 205–211. DOI:10.1073/pnas.37.4.205. PMC 1063337. PMID 14816373.
- ↑ 2,0 2,1 Cooley RB, Arp DJ, Karplus PA (2010). „Evolutionary origin of a secondary structure: π-helices as cryptic but widespread insertional variations of α-helices enhancing protein functionality”. J Mol Biol 404 (2): 232–246. DOI:10.1016/j.jmb.2010.09.034. PMC 2981643. PMID 20888342.
- ↑ Keefe LJ, Sondek J, Shortle D, and Lattman EE (2000). „The alpha aneurism: a structural motif revealed in an insertion mutant of staphylococcal nuclease”. Proc Natl Acad Sci USA 90 (8): 3275–3279. DOI:10.1073/pnas.90.8.3275. PMC 46282. PMID 8475069.
- ↑ Weaver TM (2000). „The pi-helix translates structure into function”. Protein science 9 (1): 201–206. DOI:10.1110/ps.9.1.201. PMC 2144447. PMID 10739264.
- ↑ Fodje MN, Al-Karadaghi S (2002). „Occurrence, conformational features and amino acid propensities for the pi-helix”. Protein Eng 15 (5): 353–358. DOI:10.1093/protein/15.5.353. PMID 12034854.