title: Calcium dependent conformational changes of surfactant protein A (SP-A) and its collagenase resistant fragment with or without dithiothreitol.
abstract: Calcium-dependent conformational changes of surfactant protein A (SP-A) and the collagenase resistant fragment (CRF) of SP-A were studied by measuring fluorescence spectra. The emission peaks of both SP-A and CRF in the absence of Ca2+ appeared at 343 nm when they were excited at 280 nm. In the presence of Ca2+, the peaks appeared at 340 nm and were accompanied by an increase in the fluorescence intensity. The magnitude of the fluorescence intensity change induced by Ca2+ was amplified by the addition of dithiothreitol (DTT) in both SP-A and CRF. The Ca2+ binding of CRF was measured by a flow dialysis method with 45CaCl2 in the Ca2+ concentration range where the Ca(2+)-induced fluorescence changes occurred. The maximum binding number of Ca2+ to CRF was about 2 mol per mol of CRF, and the value was independent of the presence of DTT.
authors.affiliation: Department of Biochemistry Sapporo Medical College, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Sohma
authors.forename: T
authors.initials: T
authors.lastname: Watanabe
authors.forename: Y
authors.initials: Y
authors.lastname: Kuroki
authors.forename: H
authors.initials: H
authors.lastname: Yoshino
authors.forename: N
authors.initials: N
authors.lastname: Matsushima
authors.forename: M
authors.initials: M
authors.lastname: Yazawa
authors.forename: T
authors.initials: T
authors.lastname: Akino
mesh_terms: D002118:Calcium / Q000737:chemistry*; D002413:Cations, Divalent; D017364:Collagenases / Q000378:metabolism; D004229:Dithiothreitol / Q000737:chemistry*; D006801:Humans; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D011510:Proteolipids / Q000737:chemistry*; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D002413:Cations, Divalent; D010446:Peptide Fragments; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants; D017364:Collagenases; D002118:Calcium; D004229:Dithiothreitol