Thermostability of Reovirus Disassembly Intermediates (ISVPs) Correlates with Genetic, Biochemical, and Thermodynamic Properties of Major Surface Protein mu 1

• Published in: Journal of virology Vol. 76; no. 3; pp. 1051 - 1061
• Main Authors: Middleton, J K, Severson, T F, Chandran, K, Gillian, AL, Yin, J, Nibert, M L
• Format: Journal Article
• Language: English
• Published: 01.02.2002
• Subjects: A^k1 protein; Reovirus
• ISSN: 0022-538X
• DOI: 10.1128/JVI.76.3.1051-1061.2002

Kinetic analyses of infectivity loss during thermal inactivation of reovirus particles revealed substantial differences between virions and infectious subvirion particles (ISVPs), as well as between the ISVPs of reoviruses type 1 Lang (T1L) and type 3 Dearing (T3D). The difference in thermal inactivation of T1L and T3D ISVPs was attributed to the major surface protein mu 1 by genetic analyses with reassortant viruses and recoated cores. Irreversible conformational changes in ISVP-bound mu 1 were shown to accompany thermal inactivation. The thermal inactivation of ISVPs approximated first-order kinetics over a range of temperatures, permitting the use of Arrhenius plots to estimate activation enthalpies and entropies that account for the different behaviors of T1L and T3D. An effect similar to enthalpy-entropy compensation was additionally noted for the ISVPs of these two isolates. Kinetic analyses with other ISVP-like particles, including ISVPs of a previously reported thermostable mutant, provided further insights into the role of mu 1 as a determinant of thermostability. Intact virions, which contain [varsigma]3 bound to mu 1 as their major surface proteins, exhibited greater thermostability than ISVPs and underwent thermal inactivation with kinetics that deviated from first order, suggesting a role for [varsigma]3 in both these properties. The distinct inactivation behaviors of ISVPs are consistent with their role as an essential intermediate in reovirus entry.