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Structures of intact glycoproteins from vibrational circular dichroism
Author(s) -
Shanmugam Ganesh,
Polavarapu Prasad L.
Publication year - 2006
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.20884
Subject(s) - chemistry , polyproline helix , circular dichroism , vibrational circular dichroism , glycoprotein , protein secondary structure , amide , crystallography , stereochemistry , carbohydrate conformation , peptide , nuclear magnetic resonance spectroscopy , biochemistry
Abstract Vibrational circular dichroism (VCD) spectra for the glycoproteins α 1 ‐acid glycoprotein (AGP) and bovine submaxillary mucin (BSM), have been measured in D 2 O solutions and for the films prepared from aqueous (H 2 O) buffer solutions in the 1800 to 900 cm −1 region. The solution VCD results revealed that AGP has β‐sheet structure, along with a significant amount of α‐helix as evidenced from a W pattern in the amide I region. The VCD of BSM solution suggested a polyproline II type structure, characterized by the appearance of strong negative couplet in the amide I region. The film VCD results on AGP and BSM suggested that the secondary structures of polypeptide fold in the film state are similar to those in the solution. The absence of any significant film VCD in the low frequency region (1200–900 cm −1 ), suggested that the dominant linkage for carbohydrate residues is likely to be a β linkage. VCD spectroscopy gains importance in the secondary structural analysis of polypeptide fold in glycoproteins due to the absence of interfering VCD from the carbohydrate residues in the conformationally sensitive amide I region. Also, film VCD studies permit measurements in the low wavenumber region (1200–900 cm −1 ) that reveal the dominant type of linkage for carbohydrate residues. Such clear structural information is unlike that from ECD, where ECD bands of acylated amino sugar residues interfere with those of polypeptide backbone in the conformationally sensitive far‐UV region. Proteins 2006. © 2006 Wiley‐Liss, Inc.