Members of the C-type lectin domain (CTLD) superfamily are metazoan proteins functionally important in glycoprotein metabolism, mechanisms of multicellular integration and immunity. This thesis presents the results of several computational and experimental studies of the CTLD structure, function and evolution.¶ Core structural properties of the CTLD fold were explored in a comparative analysis of the 37 distinct CTLD structures available publicly, which demonstrate significant structural conservation despite low or undetectable sequence similarity. Pairwise structural alignments of all CTLD structures were created with three different methods (DALI, CE and LOCK) and analysed manually and using a computational algorithm developed for this purpose. The analysis revealed a set of conserved positions and interactions, which were classified based on their role in CTLD structure maintenance.¶ The CTLD family is large and diverse. To organize and annotate the several thousand of known CTLD-containing protein sequences and integrate the information on their evolution, structure and function a local database and a web-based interface to it were developed. The software is written in Perl, is based on bioperl, bioperl-db and Apache::ASP modules, and can be used for collaborative annotation of any collection of phylogenetically related sequences.¶ Several studies of CTLD genomics were performed. In one such study, carried out in collaboration with the RIKEN structural genomics centre, CTLD sequences from the Caenorhabditis elegans genome were identified and clustered into groups based on similarity. The most representative members of the groups were then selected, which if characterized structurally would tell most about the C. elegans CTLDs and provide templates for homology modelling of all C. elegans CTLD structures.¶ In the other whole-genome study, the CTLD family in the puffer fish Fugu rubripes was analysed using the draft genome sequence. This work extended and complemented three genome-level surveys on human, C. elegans and D. melanogaster reported previously. The study showed that the CTLD repertoire of Fugu rubripes is very similar to that of mammals, although several interesting differences exist, and that Fugu CTLD-encoding genes are selectively duplicated in a manner suggesting an ancient large-scale duplication event. Another important finding was the identification of several new CTLDcps, which had mammalian orthologues not recognized previously.¶ CBCP, a novel CTLD-containing protein highly conserved between fish and mammals with previously unknown domain architecture, was predicted in the Fugu study based solely on ab initio gene models from the Fugu locus and cross-species genomic DNA alignments. To test if the prediction was correct, a full-length cDNA of the mouse CBCP was cloned, its tissue distribution characterized and untranslated regions determined by RACE. The full-length mCBCP transcript is 10 kb long, encodes a protein of 2172 amino acids and confirms the original prediction. The presence of a large N-terminal NG2 domain makes CBCP a member of a small but very interesting family of Metazoan proteins.

Protein Nkr-p1b is a surface receptor of cytotoxic NK cells, that mediates inhibitory signal toward the body's own cells. In this study, the ligand binding domain of the mouse protein receptor Nkr-p1b (mNkr-p1b LBD) was prepared by recombinant expression in E. coli cells. Isolated protein was subsequently used for NMR structural analysis. Prediction of protein secondary structures ratio was carried out using three different methods (CD, PSIPRED and TALOS). Results correlate well with the structure of CTLD domain, that plays a key role in ligand binding and thus to function of Nkr-p1b receptor. We managed to prepare this protein in a form suitable for NMR experiments. Based on the data obtained by NMR spectra analysis, a preliminary model of the mNkr-p1b LBD protein structure was created. However, for more precise learning of the 3D structure accurate positions of individual atoms need to be determined by other NMR spectra evaluation in the next phase. Explaining the structure of the ligand binding domain of mNkr-p1b protein could help to better understand the complex mechanism of activation of NK cell cytotoxic activity, thereby contributing to its controlled use as a therapeutic against some viral and tumor diseases.