1H, 13C and 15N NMR assignments of the C-type lectin TC14

B Chain B, Structure Of Tc14; A C-Type Lectin From The Tunicate Polyandrocarpa Misakiensis

A Chain A, Structure Of A Tunicate C-Type Lectin Complexed With D-Galactose

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Letter to the editor: 1H, 13C and 15N NMR assignments of the C-type lectin TC14.

C-type lectins are calcium-dependent carbohydrate-recognising proteins.
Isothermal titration calorimetry of the C-type Polyandrocarpa lectin (TC14)
from the tunicate Polyandrocarpa misakiensis revealed the presence of a single
calcium atom per monomer with a dissociation constant of 2.6 microM, and
confirmed the specificity of TC14 for D -galactose and related monosaccharides.
We have determined the 2.2 A X-ray crystal structure of Polyandrocarpa lectin
complexed with D -galactose. Analytical ultracentrifugation revealed that TC14
behaves as a dimer in solution. This is reflected by the presence of two
molecules in the asymmetric unit with the dimeric interface formed by
antiparallel pairing of the two N-terminal beta-strands and hydrophobic
interactions. TC14 adopts a typical C-type lectin fold with differences in
structure from other C-type lectins mainly in the diverse loop regions and in
the second alpha-helix, which is involved in the formation of the dimeric
interface. The D -galactose is bound through coordination of the 3 and
4-hydroxyl oxygen atoms with a bound calcium atom. Additional hydrogen bonds
are formed directly between serine, aspartate and glutamate side-chains of the
protein and the sugar 3 and 4-hydroxyl groups. Comparison of the galactose
binding by TC14 with the mannose binding by rat mannose-binding protein reveals
how monosaccharide specificity is achieved in this lectin. A tryptophan
side-chain close to the binding site and the distribution of hydrogen-bond
acceptors and donors around the 3 and 4-hydroxyl groups of the sugar are
essential determinants of specificity. These elements are, however, arranged in
a very different way than in an engineered galactose-specific mutant of MBPA.
Possible biological functions can more easily be understood from the fact that
TC14 is a dimer under physiological conditions.

Poget SF, Legge GB, Proctor MR, Butler PJ, Bycroft M, Williams RL. Protein Structure,
The structure of a tunicate C-type lectin from Polyandrocarpa misakiensis complexed
with D -galactose. J Mol Biol. 1999 Jul 23;290(4):867-79. PMID: 10398588; UI:
99329135

The structure of a tunicate C-type lectin from Polyandrocarpa misakiensis complexed with D -galactose.

C-type lectin TC14-1 [Polyandrocarpa misakiensis]

Structure Of A Tunicate C-Type Lectin Complexed With D- Galactose

Structure Of Tc14; A C-Type Lectin From The Tunicate Polyandrocarpa Misakiensis