Despite the known diversity among molecular components of cellulosomes, all organisms with characterized cellulosomes that we tested formed a single group distinct from organisms that lacked characterized cellulosomes or from non-cellulolytic organisms.
However, almost one-half of the predicted genes still lack characterized orthologues in other systems and for most of these genes, the function remains unknown and the gene model unconfirmed.
Although HHpred analysis was uninformative (as the high probability matches to gp41 lack characterized functions; Table 3), this protein shows similarity in BLASTP analysis to tail fiber assembly proteins of Cupriavidus necator N-1, Dickeya dadantii 3937, and Idiomarina xiamenensis 10-D-4.
RT-PCR with primers located in exon 1 and 4 revealed three aberrantly spliced mRNA species that might potentially lead to two different truncated protein fragments lacking any characterized functional domain (Supplementary Figure S1A D).
Surprisingly, a SPI-1/2 double mutant and a SPI-1/2: flhDC triple mutant, a strain lacking all characterized T3SS secretion systems, also invaded into the 3-D intestinal cells at similar levels (Figure 2E).
MO-2 is predicted to cause a frame shift that generates a stop codon at amino acid 209 and leads to a truncated peptide lacking all characterized functional domains (Fig. 6A).
While systems suggested by conserved operons are readily detected through comparative genomics resources such as STRING [ 4] and IMG [ 5], developing meaningful hypotheses for the functions of proteins lacking any characterized homolog and for the discovery and description of novel systems is non-trivial.
Notably, supergroup H is one of the largest supergroups within the NRT1/PTR family but lacks any characterized members, highlighting the need for further functional characterizations.
Thus, vinculin tail-ΔEx20 lacks the characterized interaction sites for actin filaments and, similar to vinculin-T12, shows a strongly reduced autoinhibitory head-to-tail interaction.
The shorter sequences might either lack a characterized protein domain or be too short to find statistically meaningful matches.
