– Attaches the virus to sialic acid-containing cell receptors and thereby initiating infection. Binding of HN protein to the receptor induces a conformational change that allows the F protein to trigger virion/cell membranes fusion.; Neuraminidase activity ensures the efficient spread of the virus by dissociating the mature virions from the neuraminic acid containing glycoproteins. Human parainfluenza 1 virus (HPIV-1) Hemagglutinin-neuraminidase Protein (His) is expressed in E. coli expression system with N-10xHis tag. The predicted molecular weight is 19.7 kDa and the accession number is P16071.