Lamin Loppers The nuclear lamina provides mechanical stability to the nuclear envelope and is involved in regulation of cellular processes such as DNA replication. Defects in the nuclear lamina lead to diseases such as progeria and metabolic disorders. One of the components of the nuclear lamina, lamin A, undergoes a complex maturation process. A key player is an inner nuclear membrane zinc metalloprotease (ZMP) that is responsible for two proteolysis steps (see the Perspective by Michaelis and Hrycyna ). Quigley et al. (p. 1604 ) report the crystal structure of human ZMPSTE24 and Pryor et al. (p. 1600 ) that of the yeast homolog Ste24p. The structures provide insight into the mechanism of catalysis and into why mutations in ZMPSTE24 lead to laminopathies.