The invention relates to a polypeptide capable of binding human complement component 5 (C5), said polypeptide comprising the amino acid sequence [(86) ZA 20150BM]-[L2]-QSX42X43LLX46 EAKKLX52X53X54Q wherein [(86) ZA 20150BM] is a C5 bindingmotif； [L2] is an interconnecting loop； X42 is selected from A and S； X43 is selected from N and E； X46 is selected from A, S and C； X52 is selected from E, N and S； X53 is selected from D, E and S, provided that X53 is not D when X52 is N； and X54 is selected from A and S.La invención se refiere a un polipéptido capaz de unirse al componente del complemento humano 5 (C5), tal polipéptido que comprende la secuencia de aminoácido [BM]-[L2]-QSX42X43LLX46EAKKLX 52X53X54Q en donde [BM] es un motivo de unión a C5； [L2] es un bucle de interconexión； X42 se selecciona de A y S； X43 se selecciona de N y E； X46 se selecciona de A, S y C； X52 se selecciona de E, N y S； X53 se selecciona de D, E y S, siempre que X53 no sea D cuando X52 es N； y X54 se selecciona de A y S.
