Proteins 56, 285-297 (2004)

ISSN: 1097-0134, SCI

Thermal Effects in Stretching of Go-like Models of Titin and Secondary Structures

M. Cieplak, T. X. Hoang, and M. O. Robbins

The effect of temperature on me- chanical unfolding of proteins is studied using a Go-like model with a realistic contact map and Lennard–Jones contact interactions. The behavior of the I27 domain of titin and its serial repeats is contrasted to that of simple secondary structures. In all cases, thermal fluctuations accelerate the unraveling process, decreasing the unfolding force nearly linearly at low temperatures. However, differ- ences in bonding geometry lead to different sensitiv- ity to temperature and different changes in the unfolding pattern. Due to its special native-state geometry, titin is much more thermally and elasti- cally stable than the secondary structures. At low temperatures, serial repeats of titin show a parallel unfolding of all domains to an intermediate state, followed by serial unfolding of the domains. At high temperatures, all domains unfold simultaneously, and the unfolding distance decreases monotonically with the contact order, that is, the sequence dis- tance between the amino acids that form the native contact.

DOI: 10.1002/prot.20081

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