Question

A transmembrane protein uses a β barrel structure to span the cell membrane. How can amino acid mutations in a protein within this β barrel structure affect interactions with the membrane and why?  

Answer 1

Beta barrel is a secondary structure of proteins which in most of the cases is composed of two antiparallel beta sheets, held up by H-bonds. There i tandem repeats that twists and coils to form a closed toroidal structure. The first strand and the last strand remain bonded with each other with the help of Hydrogen bonds. In the phospholipid bilayer the amino acids which composed of the transmembrane protein part is mainly composed of hydrophobic amino acids. If due to mutation hydrophobc amino acids are transformed into hydrophilic amino acids then specific interaction between amino acids will be disturbed due to creation of polar or charged amino acids interior of the hydrophobic core of plasma membrane. As a result the inter-strand interaction will be disrupted and the structure of beta barrel will no longer maintained in its native form.