Structural characterization of a highly stable cysteine protease ervatamin C.
Ervatamin C, a novel cysteine protease, belongs to alpha + beta class of proteins, probably with two domains, and retains both secondary and tertiary structures along with biological activity over a wide range of pH (2-12). Under neutral conditions, GuHCl and temperature-induced unfolding was cooperative with high transition midpoints and shows no structural changes in the presence of urea reflecting a remarkable stability. The fluorescence emission maximum at 350 nm suffers a blue shift of 4-5 nm upon lowering the pH and a red shift of 5 nm under denatured conditions. Unfolding transition curves at pH 2.0 are non-coincidental indicating the presence of intermediates in the unfolding pathway. At extremely low pH, the enzyme loses all the tertiary structure and proteolytic activity but retains a predominant secondary structure and a strong binding to ANS. GuHCl-induced unfolding of the enzyme in this intermediate state is noncooperative and indicates sequential unfolding of the domains.
Kundu
S
S
Molecular Biology Unit, Institute of Medical Sciences, Banaras Hindu University, Varanasi, 221 005, India.
Sundd
M
M
Jagannadham
M V
MV
D003546:Cysteine Endopeptidases / Q000737:chemistry*; D004795:Enzyme Stability; D010940:Plant Proteins / Q000737:chemistry*; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
D010940:Plant Proteins; D003546:Cysteine Endopeptidases; C116225:ervatamin