Secondary structure of the pore-forming colicin A and its C-terminal fragment. Experimental fact and structure prediction.

摘要: Conformational investigations, using circular dichroism, on the pore-forming protein, colicin A (Mr 60 000), and a C-terminal bromelain fragment 20 000) were undertaken to estimate their secondary structure search for pH-dependent conformational changes. Colicin peptide are mainly α-helical with an enrichment of content in domain carrying ionophoric activity. The non-negligible β-sheet is unstable easily transformed into α-helix upon decreasing polarity solvent. No evidence modification, correlated modification activity, could be obtained. estimated basis experimental data favoured model which pore built minimal number six transmembrane segements. Search such segments amino acid sequence was carried out by combining prediction methods hydrophobicity hydrophobic moment calculations. Similar calculations domains E1 IB indicate common pores formed A, IB. Only two or three putative selected sequences E1. As result, it concluded that channel probably not single molecule but more likely oligomer.