Mechanism and biological role of profilin-Srv2/CAP interaction

Profilin and cyclase-associated protein (CAP, known in yeast as Srv2) are ubiquitous and abundant actin monomer- binding proteins. Profilin catalyses the nucleotide exchange on actin monomers and promotes their addition to filament barbed ends. Srv2/CAP recycles newly depolymerized actin monomers from ADF/cofilin for subsequent rounds of polymerization. Srv2/CAP also harbors two proline- rich motifs and has been suggested to interact with profilin. However, the mechanism and biological role of the possible profilin-Srv2/CAP interaction has not been investigated. Here, we show that Saccharomyces cerevisiae Srv2 and profilin interact directly (K-D similar to 1.3 mu M) and demonstrate that a specific proline-rich motif in Srv2 mediates this interaction in vitro and in vivo. ADP- actin monomers and profilin do not interfere with each other's binding to Srv2, suggesting that these three proteins can form a ternary complex. Genetic and cell biological analyses on an Srv2 allele (srv2-201) defective in binding profilin reveals that a direct interaction with profilin is not essential for Srv2 cellular function. However, srv2-201 causes a moderate increase in cell size and partially suppresses the cell growth and actin organization defects of an actin binding mutant profilin (pfy1-4). Together these data suggest that Srv2 is an important physiological interaction partner of profilin

A high-affinity interaction with ADP-actin monomers underlies the mechanism and in vivo function of Srv2/cyclase-associated protein

Cyclase-associated protein (CAP), also called Srv2 in Saccharomyces cerevisiae, is a conserved actin monomer-binding protein that promotes cofilin-dependent actin turnover in vitro and in vivo. However, little is known about the mechanism underlying this function. Here, we show that S. cerevisiae CAP binds with strong preference to ADP-G-actin (K-d 0.02 muM) compared with ATP-G-actin (K-d 1.9 muM) and competes directly with cofilin for binding ADP-G-actin. Further, CAP blocks actin monomer addition specifically to barbed ends of filaments, in contrast to profilin, which blocks monomer addition to pointed ends of filaments. The actin-binding domain of CAP is more extensive than previously suggested and includes a recently solved beta-sheet structure in the C-terminus of CAP and adjacent sequences. Using site-directed mutagenesis, we define evolutionarily conserved residues that mediate binding to ADP-G-actin and demonstrate that these activities are required for CAP function in vivo in directing actin organization and polarized cell growth. Together, our data suggest that in vivo CAP competes with cofilin for binding ADP-actin monomers, allows rapid nucleotide exchange to occur on actin, and then because of its 100-fold weaker binding affinity for ATP-actin compared with ADP-actin, allows other cellular factors such as profilin to take the handoff of ATP-actin and facilitate barbed end assembly

Minimum inhibitory concentration of honey and borate on Candida albicans insolated from oral lesion of sub prosthetic stomatitis

https://doi.org/10.53766/ROLA/2023.18.01.02 Los tejidos bucales se encuentran expuestos a una gran variedad de elementos agresores, cuyo tratamiento odontológico implica la rehabilitación que incluye la confección de prótesis dentales. En caso de ausencias dentarias la mucosa bucal no está preparada para recibir prótesis dentales, la agresión mecánica produce acciones irritantes que conduce a la aparición de lesiones inflamatorias, donde la Candida una levadura de la microbiota habitual, puede causar estomatitis subprotésica (ESP). La medicina convencional sintética, ha sido la terapia común para el tratamiento de la estomatitis, sin embargo, dentro de las terapias alternativas naturales la miel de bórax es la fórmula oficinal antigua más utilizada, a pesar de no contar con estudios de concentración inhibitoria mínima (CIM) disponibles. El objetivo fue establecer la CIM de la miel y el borato sobre especies de C. albicans. En el siguiente trabajo se desarrolló una investigación de alcance explicativo, de diseño experimental puro. Se evaluó de manera preliminar la actividad inhibitoria de la miel y el borato al 5%,10%y 15%, utilizando la nistatina como control positivo. Posteriormente se determinó la CIM del borato y, por último, se elaboró una miel de bórax con la CIM obtenida. En los resultados la miel de abeja no presentó actividad sobre los aislados de Candida evaluados, se determinó una CIM para bórax de 256 µg/mL, excepto para los aislados C1 y C6 que presentaron colonias resistentes y para la nistatina la CIM fue 8 µg/mL. La miel de bórax preparada mantuvo las propiedades antifúngicas sobre las aislados de C. albicans evaluados. Se demostró que el efecto inhibidor del borato es similar a la nistatina y que las propiedades antifúngicas de la miel de bórax experimental se mantienen.Oral tissues are exposed to a wide variety of aggressor elements, whose dental treatment involves rehabilitation that includes the making of dental prostheses. The oral mucosa is not prepared to receive dental prostheses, mechanical aggression produces irritating actions that lead to the appearance of inflammatory lesions, where Candida, a yeast of the usual microbiota, can cause sub-prosthetic stomatitis (EPS). Synthetic conventional medicine has been the common therapy for the treatment of stomatitis, however, within the natural alternative therapies, borax honey is the most used old officinal formula, despite not having minimum inhibitory concentration studies (MIC) available.  To establish the minimum inhibitory concentration of honey and borate on species of C. albicans.  An investigation of explanatory scope, of pure experimental design, was developed. Inhibitory activity of honey and borate at 5%, 10%, 15% was preliminarily evaluated, using nystatin as a positive control. Subsequently, the MIC of borate was determined and finally, a borax honey was made with the MIC obtained. RESULTS: Bee honey did not present antifungal activity on the strains evaluated, a MIC for borax of 256 µg/mL was determined, except for strains C1 and C6 that presented resistant colonies. The MIC of the nystatin being 8 µg/mL. The prepared borax honey maintained its antifungal properties on the C. albicans strains evaluated. CONCLUSION: It was shown that the inhibitory effect of borate is similar to nystatin and that the antifungal properties of experimental borax honey are maintained