Recent Progress in Steroid Synthesis Triggered by the Emergence of New Catalytic Methods

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154510/1/ejoc201901466_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154510/2/ejoc201901466.pd

Characterization of boar sperm cytoskeletal cyclin II as an actin-binding protein

International audienc

Actin-binding properties and colocalization with actin during spermiogenesis of mammalian sperm calicin. Biol Reprod 63

The nucleus of mammalian spermatozoa is surrounded by a rigid layer, the perinuclear theca, which is divided into a suba-crosomal layer and a postacrosomal calyx. Among the proteins characterized in the perinuclear theca, calicin is one of the main components of the calyx. Its sequence contains three kelch re-peats and a BTB/POZ domain. We have studied the association of boar calicin with F-actin and the distribution of boar and human calicin during spermiogenesis compared with the distri-bution of actin. Calicin was purified from boar sperm heads un-der nondenaturating conditions. The molecule bound actin with high affinity (Kd 5;5 nM), and a stoichiometry of approxi-mately one calicin per 12 actin monomers was observed. Gel filtration studies showed that calicin forms homomultimers (tet-ramers and higher polymers). According to immunocytochemi-cal results, calicin is present (together with actin) in the acro-somal region of round spermatids and is mainly localized in the postacrosomal region of late spermatids and spermatozoa. Taken together, the results suggest that the affinity of calicin to F-actin allows targeting of calicin at the subacrosomal space of round spermatids, and that its ability to form homomultimers contrib-utes to the formation of a rigid calyx. sperm, spermatid, spermatogenesis, teste