MS07-P02 Comparison of the uridine-binding site of hexameric and heptameric archaeal Lsm proteins. Natalia Lekontceva (Institute of Protein Research RAS, Pushchino, Russia) Alisa Mikhailina (Institute of Protein Research RAS, Pushchino, Russia) Svetlana Tishchenko (Institute of Protein Research RAS, Pushchino, Russia) Alexey Nikulin (Institute of Protein Research RAS, Pushchino, Russia)email: lekontseva@vega.protres.ruThe Sm and Sm-like proteins are widely distributed among bacteria, archaea and eukarya. They are defined by the ability to adopt the Sm fold, which is comprised of a 5-stranded β-sheet and an N-terminal α-helix. They are participated in many processes connected with RNA-processing or regulation of gene expression. Hetero-heptameric eukaryotic Sm proteins form the core of the uracil-rich small nuclear RNPs that further assemble into spliceosomes and excise introns in eukaryotic pre-mRNAs. Homo-hexameric bacterial Lsm protein Hfq binds polyU RNA sequences in pockets between adjacent monomers at the central pore providing regulation translation of many mRNA. Archaeal Lsm proteins (SmAP, Sm Archaeal Protein) form homo-hexamers and homo-heptamers and appear to bind urudine-rich RNAs, nevertheless, the function of SmAP in the archaeal cells is not clear.
We compare structural organization of the uridine-binding site of SmAP from Methanococcus jannaschii, which forms hexamers, and SmAP from Methanococcus vannielii, which forms heptamers. The proteins were isolated and purified. Crystals of proteins and their complexes with ribonucleotides were obtained. Using the approach, which has been developed in our group, we analyze single-stranded RNA-binding sites on the surface of the proteins. Comparison of the obtained structures with the known SmAP structures in complex with RNA-fragments reveal significant differences in the RNA-binding site of the proteins.
This work was supported by Russian foundation for basic research (project #18-04-00222).

Keywords: Lsm protein family, archaea