Metal-free superoxide dismutase-1 and three different amyotrophic lateral sclerosis variants share a similar partially unfolded beta-barrel at physiological temperature.
The structure and unfolding of metal-free (apo) human wild-type SOD1 and three pathogenic variants of SOD1 (A4V, G93R, and H48Q) that cause familial amyotrophic lateral sclerosis have been studied with amide hydrogen/deuterium exchange and mass spectrometry. The results indicate that a significant proportion of each of these proteins exists in solution in a conformation in which some strands of the beta-barrel (i.e. beta2) are well protected from exchange at physiological temperature (37 degrees C), whereas other strands (i.e. beta3 and beta4) appear to be unprotected from hydrogen/deuterium exchange. Moreover, the thermal unfolding of these proteins does not result in the uniform incorporation of deuterium throughout the polypeptide but involves the local unfolding of different residues at different temperatures. Some regions of the proteins (i.e. the "Greek key" loop, residues 104-116) unfold at a significantly higher temperature than other regions (i.e. beta3 and beta4, residues 21-53). Together, these results show that human wild-type apo-SOD1 and variants have a partially unfolded beta-barrel at physiological temperature and unfold non-cooperatively.
Durazo
Armando
A
Department of Chemistry and Biochemistry, UCLA, Los Angeles, California 90095, USA.
Shaw
Bryan F
BF
Chattopadhyay
Madhuri
M
Faull
Kym F
KF
Nersissian
Aram M
AM
Valentine
Joan Selverstone
JS
Whitelegge
Julian P
JP
D000690:Amyotrophic Lateral Sclerosis / Q000235:genetics* / Q000378:metabolism; D018360:Crystallography, X-Ray / Q000379:methods; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods; D008670:Metals / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D013696:Temperature
D008670:Metals; D010455:Peptides; C000606290:SOD1 protein, human; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1