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Neuroglobin is a recently discovered member of the globin family, mainly observed in neurons and retina. Despite the low sequence identity (less than 20% over the whole sequence for the human proteins), the general fold of neuroglobin closely resembles that of myoglobin. The latter is a paradigmatic protein for folding studies, whereas much less is known about the neuroglobin folding pathway. | Conformational stability of neuroglobin helix F - possible effects on the folding pathway within the globin family Luca Codutti1 Paola Picotti2 f Oriano Marin2 Sylvia Dewilde3 Federico Fogolari1 Alessandra Corazza1 Paolo Viglino1 Luc Moens3 Gennaro Esposito1 and Angelo Fontana2 1 Department of BiomedicalSciences and Technologies and MATI Centre of Excellence University of Udine Italy 2 CRIBI Biotechnology Centre University of Padua Italy 3 Department of Biochemistry University of Antwerp Belgium Keywords circular dichroism globin folding myoglobin neuroglobin NMR Correspondence G. Esposito Dipartimento di Scienze e Tecnologie Biomediche University of Udine P. le Kolbe 4 33100 Udine Italy Fax 39 0432 494301 Tel 39 0432 494321 E-mail rino.esposito@uniud.it A. Fontana CRIBI Biotechnology Centre University of Padua Viale G. Colombo 3 35121 Padua Italy Fax 39 049 8276159 Tel 39 049 8276156 E-mail angelo.fontana@unipd.it tPresent address Institute of Molecular Systems Biology ETH Zurich Switzerland These authors contributed equally to this work Received 15 April2009 revised 17 June 2009 accepted 15 July 2009 Neuroglobin is a recently discovered member of the globin family mainly observed in neurons and retina. Despite the low sequence identity less than 20 over the whole sequence for the human proteins the general fold of neuroglobin closely resembles that of myoglobin. The latter is a paradigmatic protein for folding studies whereas much less is known about the neuroglobin folding pathway. In this work we show how the structural features of helix F in neuroglobin and myoglobin could represent a pivotal difference in their folding pathways. Former studies widely documented that myoglobin lacks helix F in the apo form. In this study limited proteolysis experiments on aponeuroglobin showed that helix F does not undergo proteolytic cleavage suggesting that also in the apo form this helix maintains a rigid and structured conformation. To understand better the structural .
