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N- and C-Terminal Cooperation in Rotavirus Enterotoxin: Novel Mechanism of Modulation of the Properties of a Multifunctional Protein by a Structurally and Functionally Overlapping Conformational Domain

Jagannath, MR and Kesavulu, MM and Deepa, R and Sastri, Narayan P and Kumar, Senthil S and Suguna, K and Rao, Durga C (2006) N- and C-Terminal Cooperation in Rotavirus Enterotoxin: Novel Mechanism of Modulation of the Properties of a Multifunctional Protein by a Structurally and Functionally Overlapping Conformational Domain. In: Journal of Virology, 80 (1). pp. 412-425.

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Abstract

Rotavirus NSP4 is a multifunctional endoplasmic reticulum (ER)-resident nonstructural protein with the N terminus anchored in the ER and about 131 amino acids (aa) of the C-terminal tail (CT) oriented in the cytoplasm. Previous studies showed a peptide spanning aa 114 to 135 to induce diarrhea in newborn mouse pups with the 50% diarrheal dose approximately 100-fold higher than that for the full-length protein, suggesting a role for other regions in the protein in potentiating its diarrhea-inducing ability. In this report, employing a large number of methods and deletion and amino acid substitution mutants, we provide evidence for the cooperation between the extreme C terminus and a putative amphipathic \alpha helix located between aa 73 and 85 $(AAH_7_3_-_8_5)$ at the N terminus of $\Delta N72$, a mutant that lacked the N-terminal 72 aa of nonstructural protein 4 (NSP4) from Hg18 and SA11. Cooperation between the two termini appears to generate a unique conformational state, specifically recognized by thioflavin T, that promoted efficient multimerization of the oligomer into high-molecular-mass soluble complexes and dramatically enhanced resistance against trypsin digestion, enterotoxin activity of the diarrhea-inducing region (DIR), and double-layered particle-binding activity of the protein. Mutations in either the C terminus, $(AAH_7_3_-_8_5)$, or the DIR resulted in severely compromised biological functions, suggesting that the properties of NSP4 are subject to modulation by a single and/or overlapping highly sensitive conformational domain that appears to encompass the entire CT. Our results provide for the first time, in the absence of a three-dimensional structure, a unique conformation-dependent mechanism for understanding the NSP4-mediated pleiotropic properties including virus virulence and morphogenesis.

Item Type: Journal Article
Additional Information: The copyright of this article belongs to American Society for Microbiology.
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Division of Biological Sciences > Microbiology & Cell Biology
Date Deposited: 28 Feb 2006
Last Modified: 27 Aug 2008 11:47
URI: http://eprints.iisc.ernet.in/id/eprint/5704

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