Mol Gen Genet (1981) 182:178-179 © Springer-Verlag 1981 Short Communication Revised Location of the Escherichia coli Gene Coding for Ribosomal Protein $2 Richard Lathe 1., Alex Bollen 2, and Robert Herzog 2 1 Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, U.K. z Laboratoire de G6n6tique, Universit6 Libre de Bruxelles, Rue des Chevaux 67, 1640 Rhode-St-Gen6se, Belgium Summary. P1 transduction studies of a mutation of Escherichia coli affecting the rpsB gene previously suggested the map order popC-rpsB-dapD. Biochemical analysis of transductants has now revealed that the rpsB gene lies in fact to the right hand (tsJ) side of the dapD marker. We reported recently (Bollen et al. 1979) the isolation and char- acterisation of an E. coli strain bearing a thermosensitive muta- tion, rpsB1, in the gene coding for ribosomal protein $2. P1 transduction analysis located the rpsB1 mutation between the popC and dapD markers at about 4 min on the chromosome. Conflicting data, suggesting rpsB to be located between dapD and polC (Bendiak, D., personal communication; Bendiak and Friesen, this issue) has led us to reexamine our P1 transduction data. During transduction of strain RL86 (popC50 dapD2) to pop + by a P1 lysate grown on strain RL425 (rpsB1) we observed the existence of a marker, in strain RL86, conferring thermo- sensitivity. This mutation, referred to here as nat (nutrient agar thermosensitive), has the property of conferring partial growth thermosensitivity upon nutrient agar (eg. TA12, Bollen et al. 1979) but not upon minimal agar (eg. 132, Bollen et al. 1979). The nature of the biochemical defect is unknown. The location of the nat mutation close to the dapD2 mutation of strain RL86 (see below) indicates that the strain RL58 (metB dapD2 metD279 HfrP4X) used in the original mapping may also carry this muta- tion, thus invalidating our conclusions as to the probable loca- tion of the rpsB gene. In order to determine the true location of rpsB we have now analysed popC + transductants from the cross Pl(RL425) X RL86 described above for the biochemical alteration of ribo- somal protein $2 associated with the rpsB1 mutation. Whereas the thermosensitivity on both types of media was found to be associated with loss of $2 from the ribosome (Fig. 1 ; transduc- tants 9 and 25) and thus with the rpsB1 allele (see Bollen et al. 1979), transductants exhibiting thermosensitivity on rich media alone (Fig. 1; nos. 5 and 16) were found to have a normal $2 protein. When thermosensitivity on minimal medium is thus equated with the rpsB1 mutation our transduction results may be interpreted as shown in Table 1. * Present Address: Transg6ne S.A., B.P.146, F-67028 Strasbourg Ce- dex, France Offprint requests to." R. Lathe Fig. 1. SDS-polyacrylamide gel electrophoresis of 30S ribosomal sub- unit proteins ofpopC + transductants from the cross Pl(RL425; metB rpsB1 HfrP4JO X RL86; metB popCSO dapD2 nat HfrP4X. Procedures were as described in Bollen et al., 1979. A and B are the donor and recipient strains respectively. Genotypes (phenotypes) of the transduc- tants were: 5 and 16, rpsB + nat dapD2 (thermosensitive on nutrient agar alone); 9 and 25, rpsB1 nat + dapD + or rpsB1 nat dapD+ (thermo- sensitive on both nutrient and minimal agar); 7 and 32, rpsB+ nat + dapD + (thermoresistant). Slot S contains purified $2 protein; this pro- tein is lost from the ribosome during 30S subunit purification from rpsB1 strains. Loss of $2 from the ribosome is associated with a decrease in the quantity of protein S1 (highest molecular weight band in the figure) associated with the 30S subunit (Bollen et al. 1979) The variability in the minor contaminant migrating slightly ahead is not understood popC dapD rpsB tsf ! I I I nat < 16141 < 5/41 Fig. 2. Order of genes as determined by P1 transduction. Figures give the cotransduction frequencies with the popC gene. The location of the tsf gene to the right hand side of rpsB is indicated by the results of Yamamoto et al. 1976 0026-8925/81/0182/0178/$01.00