GXSXG motif

Thioesterases of AC V synthetases differ from other thioesterases integrated in nonribosomal peptide synthetases in their direct association with an epimerase domain. A comparison of the primary sequences reveals significant differences to other NRPS thioesterases shown in Table 9. So the GXSXG motif may be involved in the control of tripeptide epimerization by selection of the isomer to be released. Finally, the data support the presence of LLL-AC V as an intermediate in penicillin biosynthesis. 

GXSXG lipase consensus sequence 8 an-kyrin repeats Ca2+-in-dependent catalytic activity, proline-rich consensus motif (PX5PX8HHPX12NX4Q), LH-iPLA 2 (long isoform, 88 kDa) but not SH-iPLA2 (short isoform, 85 kDa) is activated by ATP GDSXV modified consensus sequence of serine esterase family catalytic triad Ser-His-Asp P and y subunits form a heter-otrimer with a 45-kDa noncatalytic subunit Ca2+-indepen-dent catalytic activity 0 Ca2+-independent catalytic activity... 

Prenyl group-binding site motif, Ser-228 in GXSXG lipase consensus sequence Ca2+-independent catalytic activity... 

Fig. 1 Alignments of our sequence (top) and the sequences deposited in GenBank (bottom). Amino acids are numbered on either end and differences in AA sequences are underlined. Peptides isolated by sequencing are in hold. Symbols are located under the corresponding sequences closed triangles. Putative start of the family 1 CBM. Hatch filled boxes delineate linker regions. The GXSXG sequence of the conserved serine protease motif is enclosed in a box...

Termination of peptide synthesis is believed to involve the activity of the rhioesierase active site at the C-terminal ertd of the subunit ihar catalyzes the incorporation of the last amino acids into the peptide product. A thioe.sterase active-.site motif GXSXG, found in mammalian fiatty acid synthetase thiosterases, is also detected at the C-terminal end of SrfAC (55), GtsB (59), PvnD (27), and ACV synthetases (15). 

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