Structural requirements for processing of pro‐adipokinetic hormone I

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Abstract
We found that a seven‐residue sequence in pro‐adipokinetic hormone I (proAKH I) which precedes the endopeptidase cleavage site is predicted to form an Ω loop. Molecular modelling experiments indicated that a stable Ω loop may form at this site, and suggested that loop stability may depend on the C‐terminal loop residue, Lys12. The importance of this residue in proAKH I processing was confirmed by the observation that replacement of Lys12 by thialysine, a Lys analog with an altered side chain, prevented processing in vivo. In addition we showed by molecular modelling that this side‐chain alteration may prevent formation of an Ω loop. Together, these approaches lead us to propose that an Ω loop may serve as a recognition motif in proAKH I processing.