Temperature and salt effects on proteolytic function of turnip mosaic potyvirus nuclear inclusion protein a exhibiting a low-temperature optimum activity

Do Hyung Kim, Byoung Heon Kang, Ji Seon Han, Kwan Yong Choi

Research output: Contribution to journalArticle

3 Scopus citations

Abstract

The nuclear inclusion protein a (NIa) of turnip mosaic potyvirus is a protease responsible for processing the viral polyprotein into functional proteins. The NIa protease exhibits an unusual optimum proteolytic activity at about 16°C. In order to understand the origin of the low-temperature optimum activity, the effects of temperature and salt ions on the catalytic activity and the structure of the NIa protease have been investigated. The analysis of the temperature dependence of k(cat) and K(m) revealed that K(m) decreases more drastically than k(cat) as temperature decreases. The thermodynamic analysis showed that the decrease of K(m) is driven entropically, suggesting a possibility that the substrate binding might need a large entropy cost. The secondary structure of the NIa protease was significantly perturbed at temperatures between 20 and 40°C and the protease was unfolded at very low concentrations of guanidine hydrochloride with a transition midpoint of 0.8 M. These results suggest that the NIa protease is highly flexible in structure. Interestingly, salt ions including NaCl, KCl, CaCl2 and MgCl2 stimulated the proteolytic activity by 2-6-fold and increased the optimum temperature to 20-25°C. This stimulatory effect of the salt ions was due to the lowering of K(m). The salt ions promoted the structural rigidity as evidenced in the higher resistance to the heat-induced unfolding in the presence of the salt ions. The increase in rigidity may lead to the lowering of K(m) possibly by reducing the entropic cost for substrate binding. Taken together, these results suggest that the NIa protease is highly flexible in structure and the low-temperature optimum activity might possibly be attributed to lowered entropy cost for substrate binding at lower temperatures. Copyright (C) 2000 Elsevier Science B.V.

Original languageEnglish (US)
Pages (from-to)29-40
Number of pages12
JournalBiochimica et Biophysica Acta - Protein Structure and Molecular Enzymology
Volume1480
Issue number1-2
DOIs
StatePublished - Jul 14 2000

Fingerprint Dive into the research topics of 'Temperature and salt effects on proteolytic function of turnip mosaic potyvirus nuclear inclusion protein a exhibiting a low-temperature optimum activity'. Together they form a unique fingerprint.

  • Cite this