The purD RNA motif is a conserved RNA

RNA

Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

 structure found in epsilonproteobacteria

Epsilonproteobacteria

Epsilonproteobacteria is a class of Proteobacteria. All species of this class are, like all Proteobacteria, gram-negative.The Epsilonproteobacteria consist of few known genera, mainly the curved to spirilloid Wolinella spp., Helicobacter spp., and Campylobacter spp...

, such as the genera Helicobacter

Helicobacter

Helicobacter is a genus of Gram-negative bacteria possessing a characteristic helix shape. They were initially considered to be members of the Campylobacter genus, but since 1989 they have been grouped in their own genus...

and Campylobacter

Campylobacter

Campylobacter is a genus of bacteria that are Gram-negative, spiral, and microaerophilic. Motile, with either unipolar or bipolar flagella, the organisms have a characteristic spiral/corkscrew appearance and are oxidase-positive. Campylobacter jejuni is now recognized as one of the main causes...

. The RNA is consistently found in the apparent 5' UTR

Five prime untranslated region

A messenger ribonucleic acid molecule codes for a protein through translation. The mRNA also contains regions that are not translated: in eukaryotes these include the 5' untranslated region, 3' untranslated region, 5' cap and poly-A tail....

 of purD genes. purD genes encode the enzyme Phosphoribosylamine-glycine ligase

Phosphoribosylamine-glycine ligase

In enzymology, a phosphoribosylamine-glycine ligase is an enzyme that catalyzes the chemical reactionThe 3 substrates of this enzyme are ATP, 5-phospho-D-ribosylamine, and glycine, whereas its 3 products are ADP, phosphate, and N1-glycinamide.This enzyme belongs to the family of ligases,...

, which catalyzes an early step in de novo purine

Purine

A purine is a heterocyclic aromatic organic compound, consisting of a pyrimidine ring fused to an imidazole ring. Purines, including substituted purines and their tautomers, are the most widely distributed kind of nitrogen-containing heterocycle in nature....

 synthesis. Although a possible cis-regulatory role

Cis-regulatory element

A cis-regulatory element or cis-element is a region of DNA or RNA that regulates the expression of genes located on that same molecule of DNA . This term is constructed from the Latin word cis, which means "on the same side as". These cis-regulatory elements are often binding sites for one or...

 was proposed for this motif, experimental results indicate that it overlaps the 6S RNA

6S / SsrS RNA

6S RNA was the first noncoding RNA to be sequenced, but its function was unknown until recently. It consists of 184 nucleotides that fold into an extended hairpin structure with a large single-stranded internal bulge....

 of the relevant species, and that the second hairpin

Stem-loop

Stem-loop intramolecular base pairing is a pattern that can occur in single-stranded DNA or, more commonly, in RNA. The structure is also known as a hairpin or hairpin loop. It occurs when two regions of the same strand, usually complementary in nucleotide sequence when read in opposite directions,...

of the motif might not be biological.