▁open ▁reading ▁frames ▁( OR F s ) ▁that ▁are ▁predicted ▁to ▁encode ▁short ▁pe pt ides ▁( us ually ▁between ▁ 1 7 ▁and ▁ 1 0 0 ▁am ino ▁ac ids ). ▁One ▁of ▁the ▁OR F s ▁is ▁apparently ▁down - reg ulated ▁when ▁cells ▁are ▁grown ▁with ▁an ▁ins u fficient ▁supply ▁of ▁nit ro gen ▁sources . ▁ ▁The ▁Down stream - pe pt ide ▁mot if ▁has ▁a ▁struct ural ▁res embl ance ▁to ▁a ▁different ▁candidate ▁R NA ▁structure ▁called ▁the ▁g ln A ▁R NA ▁mot if ▁which ▁was ▁shown ▁to ▁be ▁a ▁functional ▁gl ut am ine ▁binding ▁rib os w itch ▁in ▁cy an ob acter ia . ▁The ▁most ▁striking ▁similarity ▁is ▁the ▁nucle ot ide ▁conservation ▁within ▁the ▁P 1 ▁stem ▁of ▁both ▁mot ifs , ▁and ▁this ▁and ▁other ▁similar ities ▁was ▁discussed ▁previously . ▁ ▁It ▁was ▁hypoth es ized ▁that ▁Down stream - pe pt ide ▁R N As ▁correspond ▁to ▁rib os w itch es , ▁based ▁on ▁multiple ▁lines ▁of ▁evidence . ▁ ▁First , ▁g ln A ▁R N As ▁are ▁often ▁located ▁in ▁the ▁pres umed ▁ 5 ′ ▁un trans l ated ▁regions ▁of ▁multiple ▁classes ▁of ▁gen es ▁involved ▁in ▁nit ro gen ▁met abol ism . ▁This , ▁and ▁other ▁evidence , ▁suggests ▁that ▁g ln A ▁R N As ▁are ▁rib os w itch es , ▁and ▁their ▁struct ural ▁similarity ▁to ▁Down stream - pe pt ide ▁R N