tailieunhanh - Báo cáo khoa học: Unusual stability of human neuroglobin at low pH – molecular mechanisms and biological significance

Neuroglobin (Ngb) is a recently discovered globin that is predominantly expressed in the brain, retina and other nerve tissues of human and other vertebrates. Ngb has been shown to act as a neuroprotective factor, pro-moting neuronal survival in conditions of hypoxic–ischemic insult, such as those occurring during stroke. | ỊFEBS Journal Unusual stability of human neuroglobin at low pH - molecular mechanisms and biological significance Paola Picotti1 Sylvia Dewilde2 Angela Fago3 Christian Hundahl3 Vincenzo De Filippis1 Luc Moens2 and Angelo Fontana1 1 CRIBI Biotechnology Center University of Padua Italy 2 Department of Biochemistry University of Antwerp Belgium 3 Department of Zoophysiology University of Aarhus Denmark Keywords acid stability globins limited proteolysis neuroglobin oxygen affinity Correspondence A. Fontana CRIBI Biotechnology Center University of Padua Viale G. Colombo 3 35121 Padua Italy Fax 39 49 8276159 Tel 39 49 827 6156 E-mail Present address Institute of Molecular Systems Biology ETH Zurich Switzerland Received 16 August 2009 revised 26 September 2009 accepted 30 September 2009 doi Neuroglobin Ngb is a recently discovered globin that is predominantly expressed in the brain retina and other nerve tissues of human and other vertebrates. Ngb has been shown to act as a neuroprotective factor promoting neuronal survival in conditions of hypoxic-ischemic insult such as those occurring during stroke. In this work the conformational and functional stability of Ngb at acidic pH was analyzed and the results were compared to those obtained with Mb. It was shown by spectroscopic and biochemical limited proteolysis techniques that at pH apoNgb is a folded and rigid protein retaining most of the structural features that the protein displays at neutral pH. Conversely apoMb under the same experimental conditions of acidic pH is essentially a random coil polypeptide. Urea-mediated denaturation studies revealed that the stability displayed by apoNgb at pH is very similar to that of Mb at pH . Ngb also shows enhanced functional stability as compared with Mb being capable of heme binding over a more acidic pH range than Mb. Furthermore Ngb reversibly binds oxygen at acidic pH with an affinity that increases as the