title: Penultimate proline in neuropeptides.
abstract: A recent ion mobility spectrometry-mass spectrometry (IMS-MS) study revealed that tryptic peptide ions containing a proline residue at the second position from the N-terminus (i.e., penultimate proline) frequently adopt multiple conformations, owing to the cis-trans isomerization of Xaa(1)-Pro(2) peptide bonds [J. Am. Soc. Mass Spectrom. 2015, 26, 444]. Here, we present a statistical analysis of a neuropeptide database that illustrates penultimate proline residues are frequently found in neuropeptides. In order to probe the effect of penultimate proline on neuropeptide conformations, IMS-MS experiments were performed on two model peptides in which penultimate proline residues were known to be important for biological activity: the N-terminal region of human neuropeptide Y (NPY1-9, Tyr(1)-Pro(2)-Ser(3)-Lys(4)-Pro(5)-Asp(6)-Asn(7)-Pro(8)-Gly(9)-NH2) and a tachykinin-related peptide (CabTRP Ia, Ala(1)-Pro(2)-Ser(3)-Gly(4)-Phe(5)-Leu(6)-Gly(7)-Met(8)-Arg(9)-NH2). From these studies, it appears that penultimate prolines allow neuropeptides to populate multiple conformations arising from the cis-trans isomerization of Xaa(1)-Pro(2) peptide bonds. Although it is commonly proposed that the role of penultimate proline residues is to protect peptides from enzymatic degradation, the present results indicate that penultimate proline residues also are an important means of increasing the conformational heterogeneity of neuropeptides.
authors.affiliation: †Department of Chemistry, ‡Department of Computer Science and Informatics, Indiana University, Bloomington, Indiana 47405, United States.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Glover
authors.affiliation: †Department of Chemistry, ‡Department of Computer Science and Informatics, Indiana University, Bloomington, Indiana 47405, United States.
authors.forename: Earl P
authors.initials: EP
authors.lastname: Bellinger
authors.affiliation: †Department of Chemistry, ‡Department of Computer Science and Informatics, Indiana University, Bloomington, Indiana 47405, United States.
authors.forename: Predrag
authors.initials: P
authors.lastname: Radivojac
authors.affiliation: †Department of Chemistry, ‡Department of Computer Science and Informatics, Indiana University, Bloomington, Indiana 47405, United States.
authors.forename: David E
authors.initials: DE
authors.lastname: Clemmer
mesh_terms: D000595:Amino Acid Sequence; D006801:Humans; D007536:Isomerism; D013058:Mass Spectrometry; D056004:Molecular Dynamics Simulation; D009479:Neuropeptides / Q000032:analysis* / Q000737:chemistry; D011392:Proline / Q000737:chemistry*
chemical_list: D009479:Neuropeptides; D011392:Proline