Biology subjects

Riobe, F.

Publications and source records attributed to Riobe, F..

3 recordsLinked to original sources

bioRxiv2021

De novo determination of mosquitocidal Cry11Aa and Cry11Ba structures from naturally-occurring nanocrystals

Cry11Aa and Cry11Ba are the two most potent toxins produced by mosquitocidal Bacillus thuringiensis subsp. israelensis and jegathesan, respectively. The toxins naturally crystallize within the host; however, the crystals are too small for structure determination at synchrotron sources. Therefore, we applied serial femtosecond crystallography at X-ray free electron lasers to in vivo-grown nanocrystals of these toxins. The structure of Cry11Aa was determined de novo using the single-wavelength anomalous dispersion method, which in turn enabled the determination of the Cry11Ba structure by molecular replacement. The two structures reveal a new pattern for in vivo crystallization of Cry toxins, whereby each of their three domains packs with a symmetrically identical domain, and a cleavable crystal packing motif is located within the protoxin rather than at the termini. The diversity of in vivo crystallization patterns suggests explanations for their varied levels of toxicity and rational approaches to improve these toxins for mosquito control.

molecular biology↗

bioRxiv2020

Tracking crystallophore nucleating properties: setting-up a database for statistical analysis.

In this article, the principle of a database aimed at facilitating the understanding of the unique protein nucleating properties of the Crystallophore is presented. A first analysis allows us to compare the efficiency of Tb-Xo4 with the new Lu-Xo4 variant, featuring improved phasing properties. Then, the concept of subset-of-interest is introduced to reveal potential antagonistic/synergistic effects between Tb-Xo4 and physico-chemical parameters of the crystallisation kits such as pH. The overall approach may be of interest for any studies working on solutions dedicated to improve the nucleating step in protein crystallization. TOC Graphic O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=129 SRC="FIGDIR/small/057596v1_ufig1.gif" ALT="Figure 1"> View larger version (29K): org.highwire.dtl.DTLVardef@351291org.highwire.dtl.DTLVardef@5620fcorg.highwire.dtl.DTLVardef@8fadb2org.highwire.dtl.DTLVardef@d4c208_HPS_FORMAT_FIGEXP M_FIG C_FIG SynopsisA database and associated representation tools are highlighted to understand nucleating properties of the crystallophore.

biochemistry↗

bioRxiv2020

Monitoring the production of high diffraction-quality crystals of two enzymes in real time using in situ dynamic light scattering

The reproducible preparation of well diffracting crystals is a prerequisite for every structural study based on crystallography. An instrument called the XtalController has recently been designed that allows the monitoring of crystallization assays using dynamic light scattering and microscopy, and integrates piezo pumps to alter the composition of the mother liquor during the experiment. We have applied this technology to study the crystallization of two enzymes, the CCA-adding enzyme of the psychrophilic bacterium Planococcus halocryophilus and the hen egg white lysozyme in the presence of a synthetic chemical nucleant. We were able to i) detect early nucleation events and ii) drive the crystallization system (through cycles of dissolution/crystallization) towards growth conditions yielding crystals with excellent diffraction properties. This technology opens a way to the rational production of samples for crystallography, ranging from nanocrystals for electron diffraction, microcrystals for serial or conventional X-ray diffraction, to larger crystals for neutron diffraction.

biochemistry↗