Biomedical Engineering Reference
In-Depth Information
2.2 Carbohydrate recognition domains
The carbohydrate recognition domain is highly conserved throughout different galectins
and organisms.
Fig. 2. Sequence alignment of human galectin-1, -3 and the single carbohydrate recognition
domains of galectin-8 (residues 1-150 and 221-359 of isoform a). Used sequences are
galectin-1 (NP_002296), galectin-3 (P17931) and galectin-8 isoform a (NP_963839) as
published on http://www.ncbi.nlm.nih.gov/protein. Completely conserved amino acids
are marked with an asterisk, conserved substitutions are marked with a colon and semi-
conserved substitutions with a simple dot. Important amino acids mentioned in the
following text are additionally highlighted: Conserved amino acids of the binding pocket
are highlighted in grey; residues with importance for the binding are labelled in an ellipse;
galectin-1 cysteine residues are marked with circles. The alignment has been performed
using ClustalW2 at http://www.ebi.ac.uk using the default settings (Chenna et al., 2003;
Larkin et al., 2007).
The conserved amino acids are directly involved in carbohydrate binding either by the
formation of hydrogen bonds or van der Waals interactions with the sugar moiety. Most of
the conserved amino acids form hydrogen bonds with the bound sugar unit. An important
sequence motif in this context is His(158)-Asn(160)-Arg(162) (numbering according to
human galectin-3, see Fig. 2). Those three amino acids have been found to form hydrogen
bonds with the bound galactose residue for example in galectin-1 (Lobsanov et al., 1993),
galectin-3 (Diehl et al., 2010; Seetharaman et al., 1998), and galectin-8 N-CRD (Ideo et al.,
2011; Kishishita et al., 2008) (see Fig. 3). The sequence motif can also be found in galectin-8
