title: pH-induced conformational transition of H. pylori acyl carrier protein: insight into the unfolding of local structure.
abstract: Acyl carrier protein (ACP) is a small acidic protein and its primary structure is highly conserved in various bacterial sources. Despite its small size, it interacts with diverse proteins associated with many biosynthetic pathways. The three-dimensional structure of H. pylori ACP and its structural characteristics were clarified using NMR and CD spectroscopy. H. pylori ACP consists of four helices connected by different sized loops. The helices correspond to residues L3-Q14 (alphaI), S36-G50 (alphaII), D56-E60 (alphaIII), and V65-K76 (alphaVI). The size of each helix differs slightly from that of homologous ACPs. However, H. pylori ACP showed a distinct pH-dependent conformational characteristic: at neutral pH, it adopts a partially unfolded structure, while it has a tight fold at pH 6. The chemical shift perturbation and (1)H-(15)N steady state NOE analysis at both pH 6 and 7 showed that the local change of structural components occurred mainly around loop II, and this change was reflected by the changes of the residues Ile 54 and Asp 56. Examination of the structure showed that the network of Glu 47, Ile 54, Asn 75, and Lys 76 is very important for the structural stability. The pH-dependent folding process shows a kind of cooperativity, since all the residues involved in the conformational transitions are contiguous and in spatial proximity.
authors.affiliation: National Research Laboratory (MPS), Research Institute of Pharmaceutical Sciences, College of Pharmacy, Seoul National University, San 56-1, Shillim-Dong, Kwanak-Gu, Seoul 151-742, Korea.
authors.forename: Sung Jean
authors.initials: SJ
authors.lastname: Park
authors.forename: Ji-Sun
authors.initials: JS
authors.lastname: Kim
authors.forename: Woo-Sung
authors.initials: WS
authors.lastname: Son
authors.forename: Bong Jin
authors.initials: BJ
authors.lastname: Lee
mesh_terms: D000213:Acyl Carrier Protein / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002942:Circular Dichroism; D016480:Helicobacter pylori / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D020539:Sequence Analysis, Protein
chemical_list: D000213:Acyl Carrier Protein