Mouse Hemokinin-1 Decapeptide Subjected to a Brain-specific Post-translational Modification

Reversed-phase separation of mHK-1 and SP. (A) Elution profile of synthetic mHK-1 (SRTRQFYGLM-NH2). Briefly, the peptide was eluted with a gradient of acetonitrile (dashed red line). The synthetic peptide eluted in fractions 11 and 12 (grey). Forty fractions were collected and the presence of the synthetic mHK-1 was confirmed by MALDI-ToF. The endogenous mHK-1 was separated using exactly the same instrument settings. The peptide was detected using MALDI-ToF in fraction 11 only (fraction shown in green). (B) The elution profile of synthetic SP, eluted with the same instrument settings as for mHK-1. The synthetic SP eluted in fractions 21 and 22 (grey). Endogenous SP (captured from rat brain and spleen) eluted in fraction 21 (blue).

MALDI-ToF ion spectra of mHK-1. The upper ion spectrum illustrates peaks detected in the rat spleen. The peak at m/z 1257.701 is mHK-1, and the peak at m/z 1273.697 is the oxidized form of the same peptide. The lower ion spectrum shows peaks detected in rat brain. The peak at m/z 1299.710 is acetylated mHK-1. A post-translationally modified form of endogenous mHK-1 (m/z 1299.710) corresponds to the acetylation of the N-terminal serine.