Membrane Activity of (Cys48Ser) Lung Surfactant Protein B Increases with Dimerisation
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Shahparak Zaltash
Abstract
One of the possible functions of lung surfactant protein B (SPB), an hydrophobic membraneassociated saposinlike protein, is to reduce the alveolar surface tension by promoting insertion of phospholipids into the air/liquid interface of the lung. SPB is a covalent homodimer; Cys48 of two polypeptides form an intermolecular disulphide bond. In order to test whether dimerisation of SPB is important for surfactant function, transgenic mice which express (Cys48Ser) human SPB in a mouse SPB null background were generated. In previous studies (Cys48Ser)SPB showed a concentrationdependent in vitro activity, suggesting that it may form noncovalent dimers. Here (Cys48Ser)SPB isolated from bronchoalveolar lavage of transgenic mice was studied at different concentrations by circular dichroism (CD) spectroscopy, pulsating bubble surfactometry, mass spectrometry and reversedphase HPLC. The results indicate that (Cys48Ser)SPB, both in a phospholipid environment and in organic solvents, is largely monomeric and exhibits low activity at concentrations lower than 1 2 M, while at higher concentrations it forms noncovalent dimers, which are nearly functionally equivalent to native SPB in vitro. Furthermore, electrospray mass spectrometry showed that more dimers were found relative to the monomer when the polarity of the solvent was decreased, and when the concentration of SPB increased. (Cys48Ser)SPB also eluted earlier than native SPB in reversedphase HPLC. Taken together, these results indicate that a polar surface is buried upon dimerisation, thereby promoting formation of interchain ion pairs between Glu51 Arg52 and Glu51Arg52.
Copyright © 2001 by Walter de Gruyter GmbH & Co. KG
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Articles in the same Issue
- Biological Activity of Mammalian Transcriptional Repressors
- Cloning and Characterisation of Chlorophyll Synthase from Avena sativa
- DNA Damage by 3,6-Dihydropyrazine-2,5-Dipropanoic Acid, the Cyclic Dimerization Product of 5-Aminolevulinic Acid
- Chicken Erythrocyte Pyrimidine 5-Nucleotidase: Purification and Characterization of the Subclass I Enzyme
- Coenzymes Q9 and Q10, Vitamin E and Peroxidation in Rat Synaptic and Non-Synaptic Occipital Cerebral Cortex Mitochondria during Ageing
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- Participation of Residue F552 in Domain III of the Protective Antigen in the Biological Activity of Anthrax Lethal Toxin
- Purification of Chrysancorin, a Novel Antifungal Protein with Mitogenic Activity from Garland Chrysanthemum Seeds
- Legumain Forms from Plants and Animals Differ in Their Specificity
- Assignment of the Complete Disulphide Bridge Pattern in the Human Recombinant Follitropin β -Chain
- The Small GTPase Ras Is Involved in Growth Factor-Regulated Expression of the α1 Integrin Subunit in PC12 Cells
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