A Cluster of Major Importance in the Proteobacter: ndk through engA
This cluster is almost certainly of major
importance. It is spectacularly conserved within the
Proteobacteria. In the E.coli cluster, four of the
eight genes are essential (see
Gerdes, et al).
The genes I think need to be considered are those numbered 1-8:
- 1: Putative lipoprotein precursor,
- 2: GTP-binding protein EngA [essential],
- 3: Putative inner membrane protein,
- 4: 23S rRNA methyltransferase and Florfenicol/chloramphenicol
resistance protein / Radical SAM family enzyme, UPF0063 family
- 5: Histidyl-tRNA synthetase (EC 6.1.1.21) [essential],
- 6: Nucleoside diphosphate kinase (EC 2.7.4.6) [essential],
- 7: 1-hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate synthase (EC 1.17.4.3) [essential], and
- 8: Putative membrane protein.
There are clearly more interesting genes moving in and out of the
cluster (e.g., the gene numbered 9 and annotated as Fimbrial
biogenesis and twitching motility protein PilF), but these eight
from E.coli K12 (b2511-b2518) are at
the center of things.
This level of conservation seems to suggest to me that we are looking
at something fundamentally important. I do not understand why it
should contain things that are apparently deeply connected in other
subsystems (the histidine tRNA synthetase, ndk, 1.17.4.3). However,
unraveling this cluster should lead to something important.