Pérez‐Peinado, ClaraDias, SusanaMendonça, Diogo A.Castanho, Miguel A. R. B.Veiga, Ana SaloméAndreu, David2021-10-222021-10-222019J Pept Sci. 2019 Aug;25(8):e31951075-2617http://hdl.handle.net/10451/49982© 2019 European Peptide Society and John Wiley & Sons, Ltd.Ctn[15-34], a downsized version of the snake venom cathelicidin-like peptide crotalicidin (Ctn), shows an unusually high lifespan (t1/2 , approximately 12 h) in human serum, which significantly adds to its promise as an antimicrobial and antitumor agent. Herein we investigate the role of Ctn[15-34] structure on serum survival. Using a set of analogs, we show that C-terminal amidation, as well as the specific layout of the Ctn[15-34] sequence-a helical N-terminal domain followed by a hydrophobic domain-is crucial for slow degradation, and any change in their arrangement results in significantly lower t1/2 . Aside from the privileged primary structure, features such as self-aggregation can be ruled out as causes for the long serum life. Instead, studies in other protease-rich fluids suggest a key role for certain human serum components. Finally, we demonstrate that Ctn[15-34] is able to induce bacterial death even after 12-hour pre-incubation in serum, in agreement with the proteolytic data. Altogether, the results shed light on the uncommon stability of Ctn[15-34] in human serum and confirm its potential as an anti-infective lead.engjournal article10.1002/psc.31951099-1387