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Membrane associated molecules that are probably glycoproteins could be specifically precipitated from NP-40 detergent solubilized extracts of radiolabeled mouse spleen or lymph node cells by antisera produced in congenic strain combinations differing only in the Ir gene region which is linked to the H-2 genes. These Ir region products were designated Lna (lymph node antigen) to conform to previous serological work.Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of unreduced specific immune precipitates revealed the presence of a possible dimer form, while reduced samples showed only a single peak equivalent to 30,000 daltons. Thus the Lna molecules are clearly distinct from the H-2D and H-2K molecules, which are about 45,000 daltons. Anti-Lna antibodies of different specificity can be present in a single serum; there were at least two separate antigen molecules present in one haplotype tested.

A temperature-sensitive mutant of Escherichia coli HAK88 which has been shown to have a lesion in elongation factor Ts (EFTs) was studied with repsect to its metabolism of guanosine 5'-diphosphate, 2'(3')-diphosphate (ppGpp) and the associated failure of ribosomal ribonucleic acid (rRNA) accumulation at the nonpermissive temperature. Results reported here show that (i) when EFTs is nonfunctional, a full complement of charged transfer RNA (tRNA) cannot prevent accumulation of ppGpp (magic spot) and the stringent failure of rRNA accumulation; (ii) chloramphenicol prevents magic spot (MS) formation and the stringent response not by increasing the percentage of charged tRNA, but possibly by somehow interfering directly with the synthesis of MS; and (iii) tetracycline can lead to MS disappearance without resumption of RNA synthesis. Thus, the absence of MS and the presence of a functional RNA polymerase and charged tRNA are not sufficient to support rRNA accumulation in vivo. An additional element in the regulatory system is suggested.