Caltrin of 80 aas and 1 N-terminal TMS.  Caltrin (calcium transport inhibitor) is a family of small, basic proteins of the mammalian seminal plasma which bind to sperm cells during ejaculation and inhibit the extracellular Ca²⁺ uptake, preventing the premature acrosomal exocytosis and hyperactivation when sperm cells ascend through the female reproductive tract (Grasso and Coronel 2017). It binds calmodullin but not calcium.  It also inhibits the growth of microorganisms, possibly by acting as an antibiotic, permeabilizing the bacterial membrane (Krauhs et al. 1990).