Finding step metX for L-methionine biosynthesis in Desulfovibrio vulgaris Hildenborough
No candidates for metX: homoserine O-acetyltransferase
GapMind classifies a step as low confidence even if it does not find any candidates. You can still try to find candidates by using Curated BLAST (which searches the 6-frame translation) or by text search of the annotations (which may indicate weak homology, under 30% identity or 50% coverage, that GapMind does not consider). See the links below.
Definition of step metX
- Curated proteins or TIGRFams with EC 2.3.1.31 (search)
- Comment: MetX is often found alongside a methyltransferase-like protein MetW. Because MetW is not consistently required for MetX's activity, it is not included in GapMind. Details on MetW: PMID:28581482 briefly mention that MetX proteins lacked activity when expressed in E. coli unless MetW was cloned along with it. They purified MetX by adding an N-terminal hexahistidine tag; MetW would not necessarily be purified along with it. Most likely, MetW is either modifying MetX and improving its activity, or forming a complex with MetX and stabilizing it. Mutant fitness data for MetW from various Proteobacteria shows that MetW need not be required for MetX activity (see Herbaspirillum seropedicae or Cupriavidus necator). In other organisms, MetW mutants have milder phenotypes than MetX mutants, or MetX mutants do not have a defect in some conditions, which suggests that MetW is only sometimes required (Burkholderia phytofirmans, Acidovorax 3H11, Dechlorosoma suillum PS, Marinobacter adhaerens). This might suggest that any modification has a regulatory role. In many other organisms, there is tight cofitness between MetX and MetW, suggesting that MetW is required for MetX's activity (Paraburkholderia bryophila, many Pseudomonas, Caulobacter crescentus, or Sphingomonas koreensis).
Or cluster all characterized metX proteins
This GapMind analysis is from Aug 03 2021. The underlying query database was built on Aug 03 2021.
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About GapMind
Each pathway is defined by a set of rules based on individual steps or genes. Candidates for each step are identified by using
ublast (a fast alternative to protein BLAST)
against a database of manually-curated proteins (most of which are experimentally characterized) or by using
HMMer with enzyme models (usually from
TIGRFam). Ublast hits may be split across two different proteins.
A candidate for a step is "high confidence" if either:
- ublast finds a hit to a characterized protein at above 40% identity and 80% coverage, and bits >= other bits+10.
- (Hits to curated proteins without experimental data as to their function are never considered high confidence.)
- HMMer finds a hit with 80% coverage of the model, and either other identity < 40 or other coverage < 0.75.
where "other" refers to the best ublast hit to a sequence that is not annotated as performing this step (and is not "ignored").
Otherwise, a candidate is "medium confidence" if either:
- ublast finds a hit at above 40% identity and 70% coverage (ignoring otherBits).
- ublast finds a hit at above 30% identity and 80% coverage, and bits >= other bits.
- HMMer finds a hit (regardless of coverage or other bits).
Other blast hits with at least 50% coverage are "low confidence."
Steps with no high- or medium-confidence candidates may be considered "gaps."
For the typical bacterium that can make all 20 amino acids, there are 1-2 gaps in amino acid biosynthesis pathways.
For diverse bacteria and archaea that can utilize a carbon source, there is a complete
high-confidence catabolic pathway (including a transporter) just 38% of the time, and
there is a complete medium-confidence pathway 63% of the time.
Gaps may be due to:
- our ignorance of proteins' functions,
- omissions in the gene models,
- frame-shift errors in the genome sequence, or
- the organism lacks the pathway.
GapMind relies on the predicted proteins in the genome and does not search the six-frame translation. In most cases, you can search the six-frame translation by clicking on links to Curated BLAST for each step definition (in the per-step page).
For more information, see:
If you notice any errors or omissions in the step descriptions, or any questionable results, please let us know
by Morgan Price, Arkin group, Lawrence Berkeley National Laboratory