title: Structural characterization of En-1, a cold-adapted protein pheromone isolated from the Antarctic ciliate Euplotes nobilii.
abstract: The second of two diffusible cell signal proteins (pheromones) purified from a wild-type strain of the Antarctic ciliate, Euplotes nobilii, has been determined by automated Edman degradation of the whole molecule and peptides generated by its chymotryptic digestion. The proposed sequence of 52 amino acids of this new pheromone, designated En-1, is: NPEDWFTPDT(10)CAYGDSNTAW(20)TTCTTPGQTC(30)YTCCSSCFDV(40)VGEQACQMSA(50)QC. In common with the previously determined 60-amino-acid sequence of the other pheromone, En-2, it bears eight cysteines in conserved positions (presumably linked into four conserved intrachain disulfide bonds), and physicochemical features of potential significance for cold adaptation, such as a reduced hydrophobicity, an increased solvent accessibility, and an improved local backbone flexibility. However, En-1 diverges from En-2 for having evolved a threonine cluster in the place of a glycine cluster to apparently make more flexible a region that is likely functionally important.
authors.affiliation: Dipartimento di Biologia Molecolare Cellulare e Animale, University of Camerino, Via Camerini 5, 62032 Camerino (MC), Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Alimenti
authors.forename: Claudio
authors.initials: C
authors.lastname: Ortenzi
authors.forename: Vito
authors.initials: V
authors.lastname: Carratore
authors.forename: Pierangelo
authors.initials: P
authors.lastname: Luporini
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000864:Antarctic Regions; D002918:Chymotrypsin; D016812:Euplotes / Q000378:metabolism*; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000032:analysis; D010675:Pheromones / Q000737:chemistry / Q000302:isolation & purification*; D015800:Protozoan Proteins / Q000737:chemistry / Q000302:isolation & purification*
chemical_list: D010446:Peptide Fragments; D010675:Pheromones; D015800:Protozoan Proteins; D002918:Chymotrypsin