Characterization of two crystal forms of neutrophil cationic protein NP2, a naturally occurring broad-spectrum antimicrobial agent from leukocytes.

A hexagonal crystal form (P6(3)22, a = b = 34.0 A, c = 113.5 A) and a monoclinic form (P2(1), a = 37.1 A, b = 32.2 A, c = 32.4 A, beta = 110 degrees) of neutrophil cationic protein NP2, isolated from rabbit leukocytes, have been characterized. The monoclinic form, containing two promoters (Mr = 3844) per asymmetric unit, diffracts to at least 1.8 A and is suitable for high-resolution structural studies.