The trp operon is a group of genes that are transcribed together, encoding the enzymes that produce the amino acid tryptophan in bacteria. The trp operon was first characterized in Escherichia coli, and it has since been discovered in many other bacteria. The operon is regulated so that, when tryptophan is present in the environment, the genes for tryptophan synthesis are repressed.
The Actino-pnp RNA motif is a conserved structure found in Actinomycetota that is apparently in the 5' untranslated regions of genes predicted to encode exoribonucleases. The RNA element's function is likely analogous to an RNA structure found upstream of polynucleotide phosphorylase genes in E. coli and related enterobacteria. In this latter system, the polynucleotide phosphorlyase gene regulates its own expression levels by a feedback mechanism that involves its activity upon the RNA structure. However, the E. coli RNA appears to be structurally unrelated to the Actino-pnp motif.
The Bacteroidales-1 RNA motif is a conserved RNA structure identified by bioinformatics. It has been identified only in bacteria within the order (biology) Bacteroidales. Its presumed length is marked by a promoter on one end that conforms to an alternate consensus sequence that is common in the phylum Bacteroidota, and its 3′ end is indicated by predicted transcription terminators. It is often located downstream of a gene that encodes the L20 ribosomal subunit, although it is unclear whether there is a functional reason underlying this apparent association.
The Flavo-1 RNA motif is a conserved RNA structure that was identified by bioinformatics. The vast majority of Flavo-1 RNAs are found in Flavobacteria, but some were detected in the phylum Bacteroidota, which contains Flavobacteria, or the phylum Spirochaetota, which is evolutionarily related to Bacteroidota. It was presumed that Flavo-1 RNAs function as non-coding RNAs.
The L17 downstream element RNA motif is a conserved RNA structure identified in bacteria by bioinformatics. All known L17 downstream elements were detected immediately downstream of genes encoding the L17 subunit of the ribosome, and therefore might be in the 3' untranslated regions of these genes. The element is found in a variety of lactic acid bacteria and in the genus Listeria.
The Lacto-usp RNA motif is a conserved RNA structure identified in bacteria by bioinformatics. Lacto-usp RNAs are found exclusively in lactic acid bacteria, and exclusively in the possible 5′ untranslated regions of operons that contain a hypothetical gene and a usp gene. The usp gene encodes the universal stress protein. It was proposed that the Lacto-usp might correspond to the 6S RNA of the relevant species, because four of five of these species lack a predicted 6S RNA, and 6S RNAs commonly occur in 5′ UTRs of usp genes. However, given that the Lacto-usp RNA motif is much shorter than the standard 6S RNA structure, the function of Lacto-usp RNAs remains unclear.
The Lnt RNA motif refers to a conserved RNA structure found in certain bacteria. Specifically, Lnt RNAs are known only in species within the phylum Chlorobiota, and are located in the possible 5' untranslated regions of genes that are annotated as encoding apolipoprotein N-acyltransferase enzymes. There is some doubt as to whether the indicated motif is transcribed as RNA, or whether its reverse complement is transcribed. If the reverse complement is transcribed it would potentially in 5' UTRs of genes encoding bacteriochlorophyll A, and would be close to the start codon of those genes.
The Moco-II RNA motif is a conserved RNA structure identified by bioinformatics. However, only 8 examples of the RNA motif are known. The RNAs are potentially in the 5' untranslated regions of genes related to molybdenum cofactor (Moco), specifically a gene that encodes a molybdenum-binding domain and a nitrate reductase, which uses Moco as a cofactor. Thus the RNA might be involved in the regulation of genes based on Moco levels. Reliable predictions of Moco-II RNAs are restricted to deltaproteobacteria, but a Moco-II RNA might be present in a betaproteobacterial species. The Moco RNA motif is another RNA that is associated with Moco, and its complex secondary structure and genetic experiments have led to proposals that it is a riboswitch. However, the simpler structure of the Moco-II RNA motif is less typical of riboswitches. Moco-II RNAs are typically followed by a predicted rho-independent transcription terminator.
PhotoRC RNA motifs refer to conserved RNA structures that are associated with genes acting in the photosynthetic reaction centre of photosynthetic bacteria. Two such RNA classes were identified and called the PhotoRC-I and PhotoRC-II motifs. PhotoRC-I RNAs were detected in the genomes of some cyanobacteria. Although no PhotoRC-II RNA has been detected in cyanobacteria, one is found in the genome of a purified phage that infects cyanobacteria. Both PhotoRC-I and PhotoRC-II RNAs are present in sequences derived from DNA that was extracted from uncultivated marine bacteria.
The potC RNA motif is a conserved RNA structure discovered using bioinformatics. The RNA is detected only in genome sequences derived from DNA that was extracted from uncultivated marine bacteria. Thus, this RNA is present in environmental samples, but not yet found in any cultivated organism. potC RNAs are located in the presumed 5' untranslated regions of genes predicted to encode either membrane transport proteins or peroxiredoxins. Therefore, it was hypothesized that potC RNAs are cis-regulatory elements, but their detailed function is unknown.
The psaA RNA motif describes a class of RNAs with a common secondary structure. psaA RNAs are exclusively found in locations that presumably correspond to the 5' untranslated regions of operons formed of psaA and psaB genes. For this reason, it was hypothesized that psaA RNAs function as cis-regulatory elements of these genes. The psaAB genes encode proteins that form subunits in the photosystem I structure used for photosynthesis. psaA RNAs have been detected only in cyanobacteria, which is consistent with their association with photosynthesis.
The Pseudomon-Rho RNA motif refers to a conserved RNA structure that was discovered using bioinformatics. The RNAs that conform to this motif are found in species within the genus Pseudomonas, as well as the related Azotobacter vinelandii. They are consistently located in what could be the 5' untranslated regions of genes that encode the Rho factor protein, and this arrangement in bacteria suggested that Pseudomon-Rho RNAs might be cis-regulatory elements that regulate concentrations of the Rho protein.
The radC RNA motif is a conserved RNA structure identified by bioinformatics. The radC RNA motif is found in certain bacteria where it is consistent located in the presumed 5' untranslated regions of genes whose encoded proteins bind DNA are interact with other proteins that bind DNA. These proteins include integrases, methyltransferases that might methylate DNA, proteins that inhibit restriction enzymes and radC genes. Although radC genes were thought to encode DNA repair proteins, this conclusion was based on mutation data that was later shown to affect a different gene. However, it is still possible that radC genes play some DNA-related role. No radC RNAs have been detected in any purified phage whose sequence was available as of 2010, although integrases are often used by phages.
The rne-II RNA motif is a conserved RNA structure identified using bioinformatics. It is detected only in species classified within the family Pseudomonadaceae, a group of gammaproteobacteria. rne-II RNAs are consistently located in the presumed 5' untranslated regions of genes that encode Ribonuclease E. The RNase E 5' UTR element is a previously identified RNA structure that is also found in the 5' UTRs of RNase E genes. However, the latter motif is found only in enterobacteria, and the two motifs have apparently unrelated structure. In view of their differences, it was hypothesized that rne-II RNAs fulfill the same functional role as RNase E 5' UTR elements, which is to regulate the levels of RNase E proteins by acting as a substrate for RNase E. Thus, when concentrations of RNase E are high, they will degrade their own messenger RNA.
The SAM-Chlorobi RNA motif is a conserved RNA structure that was identified by bioinformatics. The RNAs are found only in bacteria classified as within the phylum Chlorobiota. These RNAs are always in the 5' untranslated regions of operons that contain metK and ahcY genes. metK genes encode methionine adenosyltransferase, which synthesizes S-adenosyl methionine (SAM), and ahcY genes encode S-adenosylhomocysteine hydrolase, which degrade the related metabolite S-Adenosyl-L-homocysteine (SAH). In fact all predicted metK and ahcY genes within Chlorobiota bacteria as of 2010 are preceded by predicted SAM-Chlorobi RNAs. Predicted promoter sequences are consistently found upstream of SAM-Chlorobi RNAs, and these promoter sequences imply that SAM-Chlorobi RNAs are indeed transcribed as RNAs. The promoter sequences are commonly associated with strong transcription in the phyla Chlorobiota and Bacteroidota, but are not used by most lineages of bacteria. The placement of SAM-Chlorobi RNAs suggests that they are involved in the regulation of the metK/ahcY operon through an unknown mechanism.
The sucA-II RNA motif is a conserved RNA structure identified by bioinformatics. It is consistently found in the presumed 5' untranslated regions of sucA genes, which encode Oxoglutarate dehydrogenase enzymes that participate in the citric acid cycle. Given this arrangement, sucA-II RNAs might regulate the downstream sucA gene. This genetic arrangement is similar to the previously reported sucA RNA motif. However, sucA-II RNAs are found only in bacteria classified within the genus Pseudomonas, whereas the previously reported motif is found only in betaproteobacteria.
The sucC RNA motif is a conserved RNA structure discovered using bioinformatics. sucC RNAs are found in the genus Pseudomonas. They ae consistently found in possible 5' untranslated regions of sucC genes. These genes encode Succinyl coenzyme A synthetase, and are hypothesised to be regulated by the sucC RNAs. sucC genes participate in the citric acid cycle, and another gene involved in the citric acid cycle, sucA, is also predicted to be regulated by a conserved RNA structure.
The yjdF RNA motif is a conserved RNA structure identified using bioinformatics. Most yjdF RNAs are located in bacteria classified within the phylum Bacillota. A yjdF RNA is found in the presumed 5' untranslated region of the yjdF gene in Bacillus subtilis, and almost all yjdF RNAs are found in the 5' UTRs of homologs of this gene. The function of the yjdF gene is unknown, but the protein that it is predicted to encode is classified by the Pfam Database as DUF2992.
The Pedo-repair RNA motif is a conserved RNA structure identified by using bioinformatics. It has been detected in only one species of bacteria: Pedobacter sp. BAL39, within the phylum Bacteroidota. The motif might be in the 5′ untranslated regions of operons containing genes predicted to be involved in DNA repair or related to restriction enzymes.
The uup RNA motif is a conserved RNA structure that was discovered by bioinformatics. uup motif RNAs are found in Bacillota and Gammaproteobacteria.
