Spectroscopic characterization of rhinoviral protease 2A: Zn is essential for the structural integrity.
Recently, protease 2A of human rhinovirus 2 (HRV2 2A) was shown to require a zinc ion for the formation of an active enzyme although zinc is not involved mechanistically. The data presented clearly show that the zinc ion bound to a picornaviral-specific motif represents an essential component of the native structure, probably representing a new Zn-binding motif. This structure, containing mostly beta-strand elements as shown by CD spectroscopy, changes drastically upon removal of zinc. The zinc-depleted form does represent an intermediate with mostly unchanged secondary structure, but not a fully denatured random coil as obtained by guanidinium hydrochloride. This is indicated by the blue-shifted fluorescence spectra and by CD. The native protein exhibited a cooperative phase transition at 53 degrees C. In contrast, the zinc-depleted form did not show any transition at all, again demonstrating the stabilizing role of the zinc ion. A structural intermediate was observed during thermal and pH denaturation that may represent a molten globule, as suggested by its ANS binding.
Voss
T
T
Boehringer-Ingelheim Research Vienna, Austria voss@aimp.una.ac.at
Meyer
R
R
Sommergruber
W
W
D002942:Circular Dichroism; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000378:metabolism; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D011489:Protein Denaturation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence; D013329:Structure-Activity Relationship; D013816:Thermodynamics; D014508:Urea; D014764:Viral Proteins; D015032:Zinc / Q000737:chemistry* / Q000378:metabolism
D014764:Viral Proteins; D014508:Urea; D003546:Cysteine Endopeptidases; C057400:picornain 2A, Picornavirus; D015032:Zinc