Gum arabic glycoprotein is a twisted hairy rope. A new model based on O-galactosylhydroxyproline as the polysaccharide attachment site

Journal Article · Mon Jul 01 04:00:00 EDT 1991 · Plant Physiology; (United States)

DOI:https://doi.org/10.1104/pp.96.3.848· OSTI ID:5809342

Qi, Wu ^[1]; Fong, C ^[2]; Lamport, D T.A. ^[3]

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1. Beijing Agricultural Univ. (China)
2. Halfhollow Hill High School East, Dix Hills, NY (United States)
3. Michigan State Univ., East Lansing (United States)

Separation of the wound exudate from Acacia senegal (L.) Willd., gum arabic, on a preparative Superose-6 column gave two major fractions: a high molecular weight gum arabic glyco-protein (GAGP) containing about 90% carbohydrate and a lower molecular weight heterogeneous gum arabic polysaccharide fraction. Hydrogen fluoride-deglycosylation of GAGP gave a large hydroxyproline-rich polypeptide backbone (dGAGP). Alkaline hydrolysis of GAGP showed that most of the carbohydrate was attached to the polypeptide backbone as small hydroxyproline (Hyp)-polysaccharide substituents. The data imply a rodlike molecule with numerous small polysaccharide substituents (attached to 24% of the Hyp residues), regularly arranged along a highly periodic polypeptide backbone based, hypothetically, on a 10 to 12 residue repetitive peptide motif. Thus, a simple statistical model of the gum arabic glycoprotein predicts a repeating polysaccharide substituents will maximize intramolecular hydrogen bonding if aligned along the long axis of the molecule, forming in effect a twisted hairy rope. Electron micrographs of rotary shadowed GAGP molecules support that prediction and may also explain show such apparently large molecules can exit the cell by endwise reptation through the small pores of the primary cell wall.

• DOE Contract Number: AC02-76ER01338
• OSTI ID: 5809342
• Journal Information: Plant Physiology; (United States), Journal Name: Plant Physiology; (United States) Vol. 96:3; ISSN 0032-0889; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
AMINES
AMINO ACIDS
AZOLES
CARBOHYDRATES
CARBOXYLIC ACIDS
ELECTRON MICROSCOPY
GLYCOPROTEINS
GUMS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROXY ACIDS
HYDROXYPROLINE
MICROSCOPY
MOLECULAR STRUCTURE
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PEPTIDES
POLYPEPTIDES
POLYSACCHARIDES
PROTEINS
PYRROLES
PYRROLIDINES
SACCHARIDES