Structural properties of human glycodelin A in water and in water-alcohol mixtures: a comparison with bovine beta-lactoglobulin A.
Human glycodelin A (GdA) is a glycoprotein that is highly homologous to bovine beta-lactoglobulin A (beta-LgA) because the amino acid sequences are 50-60% identical. The structural characteristics of human GdA and beta-LgA were compared in water and 2-propanol/water solutions. Circular dichroism spectra reveal that in water the two proteins have a very similar beta-sheet secondary structure. In the presence of 2-propanol/water mixtures (up to 50% v/v) the alpha-helix structure of both proteins increases. A further increase in the alcohol percentage of the solvent (up to 80% v/v 2-propanol) causes the formation of a new folded tertiary structure containing mainly beta-sheet features. Synchrotron radiation small angle X-ray scattering indicates that, in a neutral pH aqueous solution, GdA is a dimer. Its radius of gyration value (Rg), 25.1+/-0.4 A, is greater than that of beta-LgA (21.1+/-0.3 A), probably because of the contribution of polysaccharides bound to Asn-28 and Asn-63 residues of GdA. Conversely, small angle X-ray scattering and gel permeation chromatography data on GdA in 2-propanol have revealed a massive aggregation of the protein.
Gaudiano
M C
MC
Dipartimento di Chimica, Università degli Studi di Roma 'La Sapienza', P.le A. Moro 5, 00185, Rome, Italy.
Pala
A
A
Barteri
M
M
D019840:2-Propanol; D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D000071816:Glycodelin; D006023:Glycoproteins / Q000737:chemistry*; D006801:Humans; D007782:Lactoglobulins / Q000737:chemistry*; D011257:Pregnancy Proteins / Q000737:chemistry*; D011487:Protein Conformation; D012995:Solubility; D012997:Solvents; D013816:Thermodynamics; D014867:Water; D014961:X-Ray Diffraction
D000071816:Glycodelin; D006023:Glycoproteins; D007782:Lactoglobulins; C045246:PAEP protein, human; D011257:Pregnancy Proteins; D012997:Solvents; D014867:Water; D019840:2-Propanol