title: Heterotypic Coiled-Coil Formation is Essential for the Correct Assembly of the Septin Heterofilament.
abstract: Protein-protein interactions play a critical role in promoting the stability of protein quaternary structure and in the assembly of large macromolecular complexes. What drives the stabilization of such assemblies is a central question in biology. A limiting factor in fully understanding such systems is the transient nature of many complexes, making structural studies difficult. Septins comprise a conserved family of guanine nucleotide binding proteins that polymerize in the form of heterofilaments. In structural terms, they have a common organization: a central GTPase domain, an N-terminal domain, and a C-terminal domain; the latter is predicted to form a coiled coil. Currently, even for the best characterized human septin heterocomplex (SEPT2/SEPT6/SEPT7), the role of C-terminal domain is not fully established, and this is partly due to the absence of electron density for the C-terminal domains in the x-ray structure. Here we present results on the homo/heterotypical affinity for the C-terminal domains of human septins belonging to the SEPT6 and SEPT7 groups (SEPT6C/8C/10C/11C and SEPT7C, respectively) and provide clear evidence that this domain determines the preference for heterotypic interactions at one specific interface during the assembly of the heterofilament. This observation has wider implications where macromolecular assemblies are defined by coiled-coil protein interactions.
authors.affiliation: Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos, Brazil; Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil.
authors.forename: Fernanda A
authors.initials: FA
authors.lastname: Sala
authors.affiliation: Departamento de Biologia Celular, Universidade de Brasília, Brasília, Brazil.
authors.forename: Napoleão F
authors.initials: NF
authors.lastname: Valadares
authors.affiliation: Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil.
authors.forename: Joci N A
authors.initials: JN
authors.lastname: Macedo
authors.affiliation: Instituto de Química de São Carlos, Universidade de São Paulo, São Carlos, Brazil.
authors.forename: Julio C
authors.initials: JC
authors.lastname: Borges
authors.affiliation: Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, Brazil. Electronic address: richard@ifsc.usp.br.
authors.forename: Richard C
authors.initials: RC
authors.lastname: Garratt
mesh_terms: D006801:Humans; D066329:Protein Aggregates; D055550:Protein Stability; D017433:Protein Structure, Secondary; D058112:Septins / Q000737:chemistry*; D013696:Temperature
chemical_list: D066329:Protein Aggregates; D058112:Septins