Septin structure and filament assembly
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Septins are able to polymerize into long apolar filaments and have long been considered to be a component of the cytoskeleton alongside intermediate filaments (which are also apolar in nature), microtubules and actin filaments (which are not). Their central guanosine triphosphate (GTP)-binding domain, which is essential for stabilizing the filament itself, is flanked by N- and C-terminal domains for which no direct structural information is yet available. In most cases, physiological filaments are built from a number of different septin monomers, and in the case of mammalian septins this is most commonly either three or four. Comprehending the structural basis for the spontaneous assembly of such filaments requires a deeper understanding of the interfaces between individual GTP-binding domains than is currently available. Nevertheless, in this review we will summarize the considerable progress which has been made over the course of the last 10 years. We will provide a brief description of each structure determined to date and comment on how it has added to the body of knowledge which is rapidly growing. Rather than simply repeat data which have already been described in the literature, as far as is possible we will try to take advantage of the full set of information now available (mostly derived from human septins) and draw the reader’s attention to some of the details of the structures themselves and the filaments they form which have not be commented on previously. An additional aim is to clarify some misconceptions.
KeywordsSeptins Filament assembly GTP-binding domain N- and C-terminal domains Interfaces Crystal structures
We would like to acknowledge the financial support of the Brazilian funding agencies CNPq, FAPESP and FAPDF. We would also like to specifically mention the dedication of students and post-docs over the last 10 years (too many to mention by name, but they know who they are) who have contributed significantly to the structural biology of septins.
Compliance with ethical standards
Conflicts of interest
Napoleão Fonseca Valadares declares that he has no conflicts of interest. Humberto d´Muniz Pereira declares that he has no conflicts of interest. Ana Paula Ulian de Araujo declares that she has no conflicts of interest. Richard Charles Garratt declares that he has no conflicts of interest.
This article does not contain any studies with human participants or animals performed by the author.
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