TABLE 1.

Properties of mutant proteins

DNA	Mean ± SD % wild-typea
	Surface expressionb	Activity
		Attachmentc	Neuraminidased
HN wild type	100	100	100
HN-I133L	127 ± 18	144 ± 21	41 ± 5
HN-L140A	118 ± 13	50 ± 4	57 ± 13

^aValues were from at least three separate experiments.

^bDetermined by FACS analysis as described in Materials and Methods.

^cDefined as the binding of avian red blood cells to monolayers of cells transfected with wild-type or mutant HN cDNAs. Binding was quantitated by measuring the hemoglobin released after lysis of the attached red blood cells.

^dNeuraminidase activity of molecules at the surfaces of transfected cells was measured as previously described (24, 26).