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There are 2.5 million cases of snakebite per year and approximately 100,000 to 150,000 deaths. Thus, it is considered an important public health problem by the World Health Organization. Snakes from the Bothrops genus may cause severe local effects in the victims, so it is important to develop inhibitors to treat local effects in patients. In addition, approximately 30 different species of bothropic snakes have been described that may present differences in their venom composition. Small structural differences in the venom proteins may result in different ligands binding. Herein, BnSP-7, a PLA-like protein that causes local myotoxic effects, was analyzed using different biophysical techniques. Crystal structures of BnSP-7 binding to three different cinnamic acid derivates were solved showing that the ligands bind in the membrane-dockage region (MDoS) of the protein. Spectroscopy fluorescence and microscale thermophoresis (MST) assays showed that these ligands also bind to BnSP-7 in solution and provide comparative information about their affinity to BnSP-7. MST experiments also showed that hydroxyl radicals of the ligands, involved in their binding with the MDoS region of BnSP-7, are essential to increase their affinity with the protein. As this region has been indicated as essential for the myotoxic mechanism, the ligands could potentially be used as inhibitors for BnSP-7. These results provide relevant insights to understand the PLA-like proteins myotoxic mechanism and may eventually lead to design of new inhibitors for these toxins. Furthermore, a comparative structural analysis of BnSP-7 with other PLA-like proteins showed that BnSP-7 has an atypical quaternary conformation, suggesting an intermediate state that is unlike other PLA-like proteins. This information, combined with the absence or partial occupancy of molecules in their hydrophobic channel and the misaligned membrane-disruption region, led us to hypothesize that the protein is not able to fully exert its myotoxic activity like other PLA-like proteins.

Telomere length maintenance is important for genome stability and cell division. In most eukaryotes, telomeres are maintained by the telomerase ribonucleoprotein (RNP) complex, minimally composed of the Telomerase Reverse Transcriptase (TERT) and the telomerase RNA (TER) components. In addition to TERT and TER, other protein subunits are part of the complex and are involved in telomerase regulation, assembly, disassembly, and degradation. Among them are some molecular chaperones such as Hsp90 and its co-chaperone p23 which are found associated with the telomerase RNP complex in humans, yeast and probably in protozoa. Hsp90 and p23 are necessary for the telomerase RNP assembly and enzyme activity. In budding yeast, the Hsp90 homolog (Hsp82) is also responsible for the association and dissociation of telomerase from the telomeric DNA by its direct interaction with a telomere end-binding protein (Cdc13), responsible for regulating telomerase access to telomeres. In addition, AAA+ ATPases, such as Pontin and Reptin, which are also considered chaperone- like proteins, associate with the human telomerase complex by the direct interaction of Pontin with TERT and dyskerin. They are probably responsible for telomerase RNP assembly since their depletion impairs the accumulation of the complex. Moreover, various RNA chaperones, are also pivotal in the assembly and migration of the mature telomerase complex and complex intermediates. In this review, we will focus on the importance of molecular chaperones for telomerase RNP biogenesis and how they impact telomere length maintenance and cellular homeostasis.

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