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17.2 A Generic Strategy for the Synthesis of Sialoconjugate Libraries  375



                                     Phe192
                                               Ser82

                    Phe193
                                  Tyr179
                                              Gln104

                                     Gly176
                           Asn175                    Thr106


                          Lys142
                                           Asp209

                            Arg173     Arg165
                                                 Asp211



               Figure 17.3  3D model of substrate-binding  All active site residues are shown that
               interactions for CSS from Neisseria meningi-  are assumed to be directly involved in
               tidis created by alignment of the X-ray pro-  binding of the CMP-Neu5Ac substrate.
               tein structure (PDB entry 1EYR [51]) with the The figure was prepared with the aid of
               CMP-Neu5Ac ligand from the corresponding  PyMOL [55].
               mouse enzyme (PDB entry 1QWJ [52]).



               100
               (%)
               40
               35
               30
               25
               20
               15
               10
                5
                0
                      WT   F192S F192S/F193Y





               Figure 17.4  Relative catalytic efficiency (k /K ) of CSS variants with different substrates
                                           cat  M
               (1,  ; 14,  ; 15,  ; 22,  ). Values are referenced to the activity of native CSS from N.
               meningitidis with its natural substrate 1, which is set at 100%.
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