Conformational transitions in N-linked oligosaccharides.

Area of Science:

• Carbohydrate Chemistry
• Structural Biology
• Biophysical Chemistry

Background:

• N-linked oligosaccharides play crucial roles in biological recognition.
• Understanding their three-dimensional structures is essential for elucidating function.
• Previous studies have lacked detailed conformational analysis of specific linkages.

Purpose of the Study:

• To develop and apply a comprehensive NMR assignment strategy for N-linked oligosaccharides.
• To investigate the conformational dynamics of specific mannose linkages (Man α1-6Man β and Man α1-6Man α).
• To identify structural determinants of oligosaccharide conformation and their relation to biological function.

Main Methods:

• Utilized a suite of 2D NMR techniques: 1H-1H correlated spectroscopy (COSY), relayed correlation spectroscopy (RECSY), nuclear Overhauser effect spectroscopy (NOESY), and triple quantum filtered correlated spectroscopy (TQCOSY).
• Integrated NMR-derived spin-spin coupling constant data with semiempirical quantum mechanical energy calculations.
• Analyzed rotamer distributions at key mannose linkages in complex, bisected complex, and oligomannose oligosaccharides.

Main Results:

• Successfully assigned six related N-linked oligosaccharides across three structural types.
• Identified specific residues that modulate the orientation of α1-6 arms, independent of oligosaccharide type.
• Demonstrated that conformational perturbations can arise from both proximal and distal residues.

Conclusions:

• The developed NMR strategy provides detailed structural insights into N-linked oligosaccharides.
• Specific glycosidic linkages exhibit distinct rotamer preferences influenced by sequence context.
• These findings contribute to understanding the molecular basis of oligosaccharide recognition in biological systems.