Histones are a family of proteins that form nucleosomes when packing DNA in the cell. The complex of histones and DNA named chromatin. In addition to histones, chromatin consists of proteins that are non-histones, which contribute to chromatin stability and gene activity. Histones, with molecular weights of 11-21 kDa, include five main classes: H1, H2A, H2B, H3, H4, forming a complex with each other by ionic bonding. The histone complex consists of (H2A-H2B) flanked with (H3-H4) tetramers. Since histones consist of basic amino acids such as arginine and lysine, they are positively charged, which facilitates binding with DNA which is negatively charged. Histones are considered antimicrobial peptides (AMPs) because they can neutralize bacterial endotoxin. The purpose of the study was to purify histones from wheat germ and characterize these, and study their effect on bacterial growth. Wheat germ was used because they are rich in chromatin. The method for isolation of histones was based on low ionic strength using three different buffers, as well as acid extraction of chromatin with sulfuric acid. To characterize histones, SDS-PAGE electrophoresis was performed and to study their bacterial inhibition, E. coli bacteria were used. The result showed a poor yield of histones, but the main classes of different histones could be separated and characterized by SDS-PAGE. Some samples showed an antibacterial effect. Optimization of the extraction is necessary to increase the yield and thus be able to better study the antibacterial effect of histones. Presumably, it is homogenization that limits the yield and possibly also modification of the acid extract to prevent aggregation.
Keywords: Antimicrobial peptides, acid extraction, chromatin, DNA, histones, ionic strength, purification, wheat germ