Identification of apolipoprotein A-I in the alpha-globulin fraction of avian plasma.
BACKGROUND
Plasma protein electrophoresis is frequently used in birds as a tool for the diagnosis and monitoring of disease. Identification of proteins in individual peaks can help improve our understanding of changes in protein concentration in physiologic and pathologic conditions.


OBJECTIVE
The aim of this study was to verify the presence and identity the protein(s) in the prominent alpha-globulin peak of orange-winged parrots (Amazona amazonica), black kites (Milvus migrans), and rock pigeons (Columba livia).


METHODS
Heparinized plasma samples were obtained from 12 birds of each species. Agarose gel electrophoresis and total protein concentration were determined using standard techniques. One plasma sample from each species was then electrophoresed using high-resolution agarose gels to isolate the alpha-globulin band. Gel strips were digested in trypsin and peptides were extracted and analyzed using liquid chromatography with tandem mass spectrometry. De novo sequencing was used to identify the protein based on homology scoring against a protein database.


RESULTS
Electrophoresis verified the presence of a single prominent alpha-globulin peak, usually in the alpha(1)-region, that had a median concentration of 9.4 g/L (range, 2.1-11.7 g/L, 21.6% of total protein) in parrots, 12.2 g/L (10.4-13.2 g/L, 35.9%) in kites, and 10.7 g/L (9.0-11.5 g/L, 40.0%) in pigeons. Mass spectrometry and sequencing analysis unequivocally identified the protein as a mature circulating form of apolipoprotein A-I (apo A-I) in all 3 species.


CONCLUSIONS
Apo A-I accounts for the prominent alpha-globulin peak and comprises a major proportion of total protein concentration in diverse avian species. As a high-density lipoprotein and negative acute phase protein with a pivotal role in cholesterol homeostasis, further study is warranted to determine the significance of changes in apo A-I concentration in avian electrophoretograms.
Roman
Yannick
Y
Le Parc de Clères, DJBZ, Muséum national d'Histoire naturelle, Clères, France. yannick.roman@cg76.fr
Bed'hom
Bertrand
B
Guillot
Alain
A
Levrier
Julie
J
Chaste-Duvernoy
Daniel
D
Bomsel-Demontoy
Marie-Claude
MC
Jalme
Michel Saint
MS
D000510:Alpha-Globulins / Q000737:chemistry*; D000595:Amino Acid Sequence; D000818:Animals; D016632:Apolipoprotein A-I / Q000032:analysis* / Q000097:blood* / Q000737:chemistry; D001717:Birds / Q000097:blood*; D002853:Chromatography, Liquid; D004586:Electrophoresis; D005260:Female; D008297:Male; D013058:Mass Spectrometry; D008969:Molecular Sequence Data
D000510:Alpha-Globulins; D016632:Apolipoprotein A-I