title: Intramolecular backfolding of the carboxyl-terminal end of MxA protein is a prerequisite for its oligomerization.
abstract: Mx proteins are large GTPases, which play a pivotal role in the interferon type I-mediated response against viral infections. The human MxA inhibits the replication of several RNA viruses and is organized in oligomeric structures. Using two different experimental approaches, the mammalian two-hybrid system and an interaction dependent nuclear translocation approach, three domains in the carboxyl-terminal moiety were identified that are involved in the oligomerization of MxA. The first consists of a carboxyl-terminal amphipathic helix (LZ1), which binds to a more proximal part of the same molecule. This intramolecular backfolding is a prerequisite for the formation of an intermolecular complex. This intermolecular interaction is mediated by two domains, a poorly defined region generated by the intramolecular interaction and a domain located between amino acids 363 and 415. Co-expression of wild-type MxA with various mutant fragments thereof revealed that the presence of the carboxyl-terminal region comprising the amphipathic helices LZ1 and LZ2 is necessary and sufficient to exert a dominant negative effect. This finding suggests that the functional interference of the carboxyl-terminal region is due to competition for binding of an as yet unidentified cellular or viral target molecules.
authors.affiliation: Institute of Medical Virology, University of Zürich, CH-8028 Zürich, Switzerland.
authors.forename: C
authors.initials: C
authors.lastname: Di Paolo
authors.forename: H P
authors.initials: HP
authors.lastname: Hefti
authors.forename: M
authors.initials: M
authors.lastname: Meli
authors.forename: H
authors.initials: H
authors.lastname: Landis
authors.forename: J
authors.initials: J
authors.lastname: Pavlovic
mesh_terms: D016475:3T3 Cells; D000818:Animals; D019204:GTP-Binding Proteins; D006801:Humans; D007930:Leucine / Q000737:chemistry; D051379:Mice; D064547:Myxovirus Resistance Proteins; D009842:Oligopeptides; D010455:Peptides / Q000737:chemistry; D010641:Phenotype; D011108:Polymers; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*
chemical_list: C579071:MX1 protein, human; C579070:Mx1 protein, mouse; D064547:Myxovirus Resistance Proteins; D009842:Oligopeptides; D010455:Peptides; D011108:Polymers; D011506:Proteins; C085706:FLAG peptide; D019204:GTP-Binding Proteins; D007930:Leucine