Fig. 3

Structural features of the chitin synthase proteins. The core of CHS proteins is always composed of conserved motifs named a-h and playing a role in the active site of the enzyme (Additional file 7: Figure S3). The domains related to chitin synthase used for their detection, Chitin_synth_1 (PF01644) and Chitin_synth_2 (PF03142), correspond to the a-c and a-h regions respectively. Other domains from the Pfam library, 1N (Chitin_synth_1N; PF08407), Aminotransferase (DegT_DnrJ_EryC1; PF01041), Myosin head (Myosin_head; P00063), C5 (Cyt-b5; PF00173) and D (DEK_C; PF08766) were often detected in some CHS clades and are indicated by dashed boxes. The length variation of the myosin head domain in the clade V is represented by a dashed line in the dashed box of this domain. N-terminal and C-terminal regions of CHS are variable and transmembrane segments detected in almost all the sequences of one clade are shown with black solid squares. The less frequent additional segments are shown with white solid squares. Predicted outside or cytoplasmic localizations of eukaryota CHS protein segments are indicated thanks to a dotted line (or periplasmic and cytoplasmic localizations for bacterial CHS and HAS). Cytoplasmic localization of the conserved motifs a-h in homologous GT2 glycosyltransferases was confirmed with LacZ, PhoA and/or GFP reporter fusions [105–109]. According to these studies, some predicted transmembrane domains are, in fact, putative membrane domains that do not cross the membrane (black circles or white circles for the less frequent ones). The distant motif h might interact with the other conserved motifs as its cytoplasmic localization was confirmed