Secretory proteins as potential semiochemical carriers in the horse.
Two soluble proteins were isolated as major secretory products of horse sweat and of the parotid gland and characterized for structural and functional properties. The first protein, lipocalin allergen EquC1, was characterized for its glycosylation sites and bound glycosidic moieties. Only one (Asn53) of the two putative glycosylation sites within the sequence was post-translationally modified; a different glycosylation pattern was determined with respect to data previously reported. When purified from horse sweat, this protein contained oleamide and other organic molecules as natural ligands. Ligand binding experiments indicated good protein selectivity toward volatile compounds having a straight chain structure of 9-11 carbon atoms, suggesting a role of this lipocalin in chemical communication. The second protein, here reported for the first time in the horse, belongs to the group of parotid secretory proteins, part of a large superfamily of binding proteins whose function in most cases is still unclear. This protein was sequenced and characterized for its post-translational modifications. Of the three cysteine residues present, two were involved in a disulfide bridge (Cys155-Cys198). A model, built up on the basis of similar proteins, indicated a general fold characterized by the presence of a long hydrophobic barrel. Binding experiments performed with a number of different organic compounds failed to identify ligands for this protein with a well-defined physiological role.
D'Innocenzo
Barbara
B
Dipartimento di Chimica e Biotecnologie Agrarie, Università di Pisa, 56124 Pisa, Italy.
Salzano
Anna Maria
AM
D'Ambrosio
Chiara
C
Gazzano
Angelo
A
Niccolini
Alberto
A
Sorce
Carlo
C
Dani
Francesca Romana
FR
Scaloni
Andrea
A
Pelosi
Paolo
P
D000595:Amino Acid Sequence; D000818:Animals; D002352:Carrier Proteins / Q000302:isolation & purification* / Q000378:metabolism; D005260:Female; D006023:Glycoproteins / Q000302:isolation & purification*; D006736:Horses / Q000502:physiology*; D054834:Lipocalins; D008297:Male; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010675:Pheromones / Q000378:metabolism; D017510:Protein Folding; D012471:Salivary Proteins and Peptides / Q000302:isolation & purification*; D016415:Sequence Alignment; D013542:Sweat / Q000737:chemistry
D002352:Carrier Proteins; C103025:Equ c1 allergen, Equus caballus; D006023:Glycoproteins; D054834:Lipocalins; D010675:Pheromones; D012471:Salivary Proteins and Peptides