Chimeric receptor binding proteins resistant to proteolytic degradation

A chimeric receptor binding protein (RBP) resistant to proteolytic digestion,

• wherein said chimeric RBP comprises an N-terminal region of a side tail fiber (STF) protein from a lambdoid bacteriophage, fused through a designed linker region consisting of 1 to 70 amino acids or 1 to 30 amino acids, to a C-terminal region of a RBP protein from a different bacteriophage, wherein said N-terminal region and C-terminal region are fused within a site of the N-terminal STF region, called insertion site, having at least 80% identity with a site selected from the group consisting of amino acids SAGDAS (SEQ ID NO:
• 1), ADAKKS (SEQ ID NO:
• 2), MDETNR (SEQ ID NO:
• 3), SASAAA (SEQ ID NO:
• 4), and GAGENS (SEQ ID NO:
• 5);
• and
• (i) wherein said N-terminal region or said C-terminal region comprises the sequence of the linker region, said sequence being identical to the corresponding sequence in the N-terminal region or C-terminal region of the RBP from which it is derived, and said sequence restoring resistance to proteolytic digestion to said chimeric RBP compared to a chimeric RBP only differing by the absence of said linker region, and wherein said designed linker region comprises, or consists of, the amino acid sequence GSATDVMIQL (SEQ ID NO:
• 6) or GSATDVMIQLA (SEQ ID NO:
• 7);
• or
• (ii) wherein said designed linker region comprises or consists of an heterologous amino acid sequence which is not from one of the RBP from which the N-terminal region and the C-terminal region of the chimeric RBP are derived, and wherein said designed linker region comprises, or consists of, the amino acid sequence of SEQ ID NO:
• 34 or SEQ ID NO:
• 36 wherein said designed linker region comprises a helix or helical bundle and wherein said linker region is designed to be resistant to proteolytic digestion.

A chimeric receptor binding protein (RBP) resistant to proteolytic digestion, wherein said RBP comprises a portion of a receptor binding protein from a bacteriophage fused through a designed linker region consisting of 1 to 70 amino acids, to a portion of a receptor binding protein from a different bacteriophage, wherein said linker region is designed to be resistant to proteolytic digestion, wherein said chimeric RBP comprises, or consists of, the sequence of SEQ ID NO:

• 9, SEQ ID NO:
• 10, SEQ ID NO:
• 11, SEQ ID NO:
• 13, SEQ ID NO:
• 14, SEQ ID NO:
• 38 or SEQ ID NO:
• 40.