Avtor/Urednik		Žerovnik, Eva; Cimerman, Nina; Kos, Janko; Turk, Vito; Lohner, Karl
Naslov		Thermal denaturation of human cystatin C and two of its variants; comparison to chicken cystatin
Tip		članek
Vir		Biol Chem
Vol. in št.		Letnik 378
Leto izdaje		1997
Obseg		str. 1199-203
Jezik		eng
Abstrakt		Thermal denaturation of the recombinant human cystatin C, an 8-residue shorter variant (Leu-9 cystatin C), and the W1065 mutant were measured using differential scanning calorimetry (DSC). The finding that Leu-9 cystatin C is of similar stability to the full length protein is in accordance with its nearly normal inhibitory activity. The variant W1065 cystatin C exhibits a higher melting temperature by 4 degrees than the wild-type protein. This contrasts with its reduced inhibitory activity and represents an example where activity changes are due to local effects and are not correlated to stability. From the ratio between Van't Hoff and calorimetric enthalpies it is judged that recombinant human cystatin C and Leu-9 cystatin C are dimeric prior to thermal unfolding whereas W1065 cystatin C is monomeric. Melting temperatures and estimated stabilities for some other members of the cystatin superfamily of the cysteine proteinase inhibitors are presented which have been recorded previously or were collected for this study (chicken cystatin). It is concluded that thermal stability of human cystatin C (Tm = 82 degree) is placed in between the more stable human stefin A (Tm= 95 degree) and the less stable human stefin B (Tm = 66 degree) whereas chicken cystatin behaves as a thermophilic protein, meiting above 115 degree. To illustrate secondary structure changes, thermal denaturations of the recombinant human cystatin C and of W1065 cystatin C were foilowed by circular dichroism in the far UV It was found that the change in tertiary structure (revealed by DSC) precedes the major change in secondary structure.
Deskriptorji		CYSTATINS CYSTEINE PROTEINASE INHIBITORS PROTEIN DENATURATION TEMPERATURE CHICKENS