1OQL

Mistletoe Lectin I from Viscum album complexed with galactose

Summary for 1OQL

• Entry DOI: 10.2210/pdb1oql/pdb
• Descriptor: MISTLETOE LECTIN I, 2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose, 2-acetamido-2-deoxy-beta-D-glucopyranose, ... (6 entities in total)
• Functional Keywords: type-ii ribosome-inactivating protein, ricin-like, beta-trefoil, hydrolase-sugar binding protein complex, hydrolase/sugar binding protein
• Biological source: Viscum album (European mistletoe); More
• Total number of polymer chains: 2
• Total formula weight: 58352.29

Authors

Niwa, H.,Tonevitsky, A.G.,Agapov, I.I.,Saward, S.,Pfuller, U.,Palmer, R.A. (deposition date: 2003-03-10, release date: 2003-07-01, Last modification date: 2024-10-23)

Primary citation

Niwa, H.,Tonevitsky, A.G.,Agapov, I.I.,Saward, S.,Pfuller, U.,Palmer, R.A.
Crystal structure at 3 A of mistletoe lectin I, a dimeric type-II ribosome-inactivating protein, complexed with galactose
EUR.J.BIOCHEM., 270:2739-2749, 2003

PubMed Abstract: The X-ray structure of mistletoe lectin I (MLI), a type-II ribosome-inactivating protein (RIP), cocrystallized with galactose is described. The model was refined at 3.0 A resolution to an R-factor of 19.9% using 21 899 reflections, with Rfree 24.0%. MLI forms a homodimer (A-B)2 in the crystal, as it does in solution at high concentration. The dimer is formed through contacts between the N-terminal domains of two B-chains involving weak polar and non-polar interactions. Consequently, the overall arrangement of sugar-binding sites in MLI differs from those in monomeric type-II RIPs: two N-terminal sugar-binding sites are 15 A apart on one side of the dimer, and two C-terminal sugar-binding sites are 87 A apart on the other side. Galactose binding is achieved by common hydrogen bonds for the two binding sites via hydroxy groups 3-OH and 4-OH and hydrophobic contact by an aromatic ring. In addition, at the N-terminal site 2-OH forms hydrogen bonds with Asp27 and Lys41, and at the C-terminal site 3-OH and 6-OH undergo water-mediated interactions and C5 has a hydrophobic contact. MLI is a galactose-specific lectin and shows little affinity for N-acetylgalactosamine. The reason for this is discussed. Structural differences among the RIPs investigated in this study (their quaternary structures, location of sugar-binding sites, and fine sugar specificities of their B-chains, which could have diverged through evolution from a two-domain protein) may affect the binding sites, and consequently the cellular transport processes and biological responses of these toxins.

PubMed: 12823544
DOI: 10.1046/j.1432-1033.2003.03646.x

Experimental method

X-RAY DIFFRACTION (3 Å)