Archive | 2019
Estudos estruturais de hidrolases de glicosídeos em solução usando técnicas de espalhamento a baixo ângulo (SAS)
Abstract
Structural studies of glycoside hydrolyses in solution using small-angle scattering (SAS) techniques The Glycoside Hydrolases (GHs) play a key role in a number of biomedical processes and industrial applications. Most of these enzymes are multidomain proteins composed of different functional domains connected by linker peptides. Thus, it is very important to determine structural organization of glycoside hydrolases in terms of positions and orientations of their individual domains and comprehend the interplay between their multiple domains under close-to physiological conditions. To study the glycoside hydrolases, in this work a small-angle scattering method has been used. Currently, the conformation, dynamics and function of GHs with multiple domains are not fully understood. This is why the information on their structural organization and mobility; mutual position and orientation of the individual domains and conformational changes induced by interaction with the substrates or difference in biochemical conditions might be very informative. A large number of GHs have been cloned and expressed in the lab under direction of Prof. Dr. Igor Polikarpov (Molecular Biotechnology group, IFSC/USP) and we follow already established protocols for their expression and purification. SAXS experiments have been carried out in collaboration with Dr. Evandro Ares de Araujo (USP, São Carlos) and Prof. Dr. Mario de Oliveira Neto (UNESP, Botucatu). Additionally to experimental work, a new software package SAXSMoW2 for SAXS data processing has been developed. The software allows to obtain rapidly main structural parameters of the protein molecule, calculate molecular weight and oligomeric state. To supplement an structural data, the method of statistical coupling analysis (SCA) has been significantly improved and applied. The method allows a better understanding of interconnection between evolutionary caused structural features and their biological functionality. Also, various bioinformatic methods were developed to complete and understand better structural information obtained in SAXS experiments. The first one is a method for separating sequences from GH7 into the two bins of exoand endogluconases. It is helpful to analyze each type of proteins inside the family separately and study the role of functional loops -structural features that significantly influence on biological activity. Other developed method is for finding of activity center in the new obtained Xylose Isomerase enzyme using related well-known structure from the same family. This method was applied to the enzyme whose structure was studied using crystallography technique in our laboratory at IFSC/USP. Inspired by SCA, a method of aminoacid fuzzy communities detection in proteins has been developed as well. This information also can complete SCA results showing strong correlated sets of aminoacids in the enzyme. Another one new developed method is an estimation of carbohydrate-active family affiliation of unknown proteins using Markov hidden model similarities and open access databanks of protein sequences.