Single domain binding molecule

A single domain specific binding molecule having the structure

• FW1-CDR1-FW2-HV2-FW3a-HV4-FW3b-CDR3-FW4
• in which the Framework Regions FW1, FW2, FW3a, FW3b, and FW4, the Complementarity Determining Regions CDR1 and CDR3, and the Hypervariable Regions HV2, and HV4 have amino acid sequences in which
• FW1 comprises TRVDQTPRTATRETGESLTINCVLT,
• FW2 comprises TYWYRKNPGS,
• FW3a comprises GRYVESVN,
• FW3b comprises FSLRIKDLTVADSATYICRA,
• FW4 comprises GAGTVLTVN,
• CDR1 comprises DTSYPLYS,
• CDR3 comprises
• (i) MGTNIVVTGD,
• (ii) MATNIWTGD, MGTDSWTGD, MGTNSWTGD, MSTNIWTGD, ITTDSWTSD, MGANSWTGD, MGTNGWTGD, SDIAMGTYD, ITTHSWSGD, LSTYMEAGD, MDTSAGVVD,
• (iii) ESPPICTSQGIAAVTKYYD, YTIHIKLEXH, HAGYGVWNRGLQWRGYDXYD, YTPGREDY, EKGRKGSAITSCRRSSYYD, QSLAISTRSYWYD, or
• (iv) GVAGGYCDYALCSSRYAE,
• HV2 comprises SNKEQISIS,
• HV4 comprises KGTKS,
• or a sequence having at least 50% identity thereto, where the amino acid residue “X” represents glutamine (Q).