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Structural studies of septin heteromeric coiled-coils by nuclear magnetic resonance spectroscopy

Grant number: 18/19992-7
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): February 01, 2019
Effective date (End): January 31, 2021
Field of knowledge:Biological Sciences - Biophysics - Molecular Biophysics
Principal Investigator:Richard Charles Garratt
Grantee:Italo Augusto Cavini
Home Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil

Abstract

Septins constitute a conserved guanine-binding protein family which are involved in several cellular processes and are capable of self-assembling into heterofilaments and high-order complexes. The human septins are encoded by 13 different genes and are divided into four groups based on their similarity. The C-terminal domain of septins contains characteristic repeats of alpha-helix coiled-coils whose importance in the formation and/or maintenance of complexes is still not fully understood. To date, the first and only crystallographic structure of a septin heterocomplex, the heterofilament SEPT2-6-7 published in 2007, does not contain information on the C-terminal domains - because of the absence of electron density in these regions. The current project proposes to obtain structural information on the C-terminal domains of SEPT6 (and others of its group as SEPT8, 10, 11 and 14) and SEPT7 using nuclear magnetic resonance and X-ray crystallography techniques. Among our objectives, we aim to determine interaction patterns that stabilize the interface of the SEPT6C-7C coiled-coil heterodimer and give selectivity to the heterofilament assembly. With nuclear magnetic resonance spectroscopy, we expect to obtain eNOEs, interproton distances up to 5 Å, that will indicate the relative orientation of the heterodimer and allow solving its structure in solution. In parallel, crystallographic assays will be performed to obtain a three-dimensional model also by X-ray diffraction. A better structural knowledge of the C-terminal domains will certainly shed light on how septins organize and also on the reason why different isoforms exist in some organisms.