A specific ribonucleoprotein fragment from Escherichia coli 30-S ribosomes. Location of the RNA component in 16-S RNA.

Abstract

32P‐labelled ribosomal sub‐particles were hydrolysed with ribonuclease T1, under conditions which have previously been shown to yield a specific fragment of RNA · protein (“band III”), containing only four of the 21 30‐S ribosomal proteins. The hydrolysate was fractionated on a polyacrylamide gel using the methods already published, and gel fractions containing the specific RNA · protein fragment were subjected to electrophoresis on a second polyacrylamide gel, in the presence of sodium dodecylsulphate to dissociate RNA and protein. Two bands of [32P]RNA were reproducibly observed, containing about 320 and 360 nucleotides, respectively. Two‐dimensional fingerprints of ribonuclease T1, hydrolysates from both these RNA species showed that the two fragments were almost identical. Oligonucleotides from the fingerprints were digested with pancreatic ribonuclease, and the secondary digestion products analysed and compared with the known sequence of 16‐S ribosomal RNA. Several characteristic oligonucleotides from regions D, E and P of the RNA were identified unambiguously. Other oligonucleotides were found which could have arisen from more than one part of the 16‐S RNA, but in each case one of the possibilities was in regions D, E, E′ or P. It was concluded that the band III proteins are associated with these contiguous regions of the 16‐S RNA, i.e. near to its 3′‐end.