Breakthrough in the precision engineering of four-stranded beta-sheets

In addition to the natural sequence of the amino acids that make up a protein, their three-dimensional arrangement in space is also critical to its function. For example, β-sheets are sheet-like structures formed through hydrogen bonds between adjacent peptide chains and play a crucial role in protein stability and folding. They have also been linked to various neurodegenerative diseases, including Alzheimer’s disease. On the other hand, β-sheet engineering has potential applications in biotechnology, medicine, and nanomaterials science.

Unfortunately, producing β-sheet assemblies with precisely controlled numbers of strands is quite challenging for two reasons. First, multi-stranded β-sheets tend to aggregate into aggregates called fibrils, which can easily become insoluble and alter or negate their biological function. Second, when peptide chains are combined during β-sheet synthesis, many structural isomers may arise. This means that the resulting assemblies often have unpredictable chain orientations, arrangements, or numbers, making it difficult to produce only a specific target compound. For these reasons, a new method of creating customized β-sheets is needed.

In a recently published study Applied Chemistry International Edition On October 22, 2024, a research team led by Tomohisa Sawada, associate professor at the Tokyo Institute of Science (Science Tokyo), Japan, set out to find solutions to these problems. As reported in their study, they developed a promising method to produce four-stranded β-sheets using silver atoms as metallopeptide coordination centers.

Researchers designed a pentapeptide, simply called “1,’where the second and fourth residues are 3-pyridyl-substituted alanine residues. The pyridyl groups introduced on opposite sides of the main chain serve as metal complexing sites for silver atoms. After adding silver (Ag), two ‘1‘The molecules will combine to form Ag₂(1)₂ rings as hypothesized intermediates. Interestingly, due to the reversibility of metal coordination during the reaction, Ag is₂(1)₂ The rings end up in an interlocked state, with hydrogen bonds between adjacent pentapeptides holding the entire β-sheet structure together.

The team confirmed the successful synthesis of these interlocking structures, [Ag₂(1)₂]₂measured by NMR and X-ray crystallography. Most notably, the resulting four-stranded β-sheet converges into a single type of isomeric structure without aggregation. Simply put, all beta strands are made up of two interlocking rings, with the first and third strands pointing in one direction and the second and fourth strands pointing in the other direction. The relative positions of the interlocking metal complexing sites in all resulting β-strands are also the same. “Our results show that the combination of β-sheet hydrogen bond formation and side chain metal cross-links limits the number of possible isomers. In other words, we show that non-covalent side chain cross-links can induce a high degree of selectivity of single isomers to build β-sheets in discrete forms,” ​​commented Sawada.

The results presented in this study could make it easier to study β-sheets, thereby unlocking their potential in next-generation biotechnology and nanotechnology. “To our knowledge, this is the first example of the precise construction of a four-stranded β-sheet through non-covalent interactions alone. We believe that our efforts pave the way for the rational construction of β-sheet structures and their utility in the future. effect,” concluded Sawada, who is excited about the possibility.