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Peptide studies on two acidic proteins, A1 and A2, from 50-S ribosomes of Escherichia coli indicate a closely related primary structure. 1. Amino acid compositions of the tryptic peptides of the two proteins are identical, with exception of the amino terminal peptide. 2. The N-terminal amino acid sequence of A2-protein is Ser-Ile-Thr-Lys, while that of A1-protein is N-acetyl-Ser-Ile-Thr-Lys. 3. The estimated number of 120 amino acid residues in each polypeptide chain is consistent with the physical molecular weight estimate. 4. In 50% of the polypeptide chains, in both A1- or A2-protein, a specific lysine residue is replaced by ε-N-monomethyl-lysine. [ABSTRACT FROM AUTHOR]

16-S RNA and five pure ribosomal proteins (S3, S4, S6, S7 and S8) from Escherichia coli 30-S subunits were studied by circular dichroism in regard to the reconstitution of biologically active subunits. A small structural variation upon heating could be measured for RNA. It cannot be interpreted in terms of stacking or disruption of hydrogen bonds. However, most proteins underwent important structural modifications when heated to 42 °C in reconstitution solvent. This effect was not dependent on the presence of magnesium salt. The relative amounts of secondary structure of native and heat-denatured ribosomal proteins were calculated by using three reference curves obtained from standard proteins, the exact secondary structure of which has been determined by X-ray crystallography. In contrast with earlier results, about 18 %, β-structure was detected in native proteins. This discrepancy can most probably be attributed to the calculation method used. Results are discussed in relation to reconstitution of ribosomes. [ABSTRACT FROM AUTHOR]

Application of the two-dimensional polyacrylamide gel electrophoretic procedure recently described by Mets and Bogorad [4] to the resolution of Escherichia coli ribosomal proteins is described. This procedure is fast (running time of 8-10 h) and highly sensitive (1-2 µg protein per spot) and it gave good resolution for the majority of the 55 proteins in E. coli ribosomes. Moreover, the method has permitted the resolution of a large number of high-molecular-weight. proteins associated with ribosomes not exposed to high-salt washing. Using purified proteins, the positions in the electrophrogram of the individual proteins of the 30-S subunit have been determined. [ABSTRACT FROM AUTHOR]

We are searching for biochemical events related to the process of bacterial division. Data obtained with intact bacteria, using inhibitors primarily, august that protein synthesis must occur through most of the division cycle in order that a bacterium can divide at the end of the cycle. Hence, one approach is to look for a protein that Is made throughout the division cycle and whose production is related to ability of the bacteria to divide. Dr Masayorl Inouye modified the ability of the bacterium Escherichia coli to divide, using mutants, inhibitors or nutritional deficiencies, and then looked for alterations in the pattern formed by electropharesis of membrane proteins on polyacrylamide gels. One protein peak on the gels was strongly increased whenever the cells Were prevented from dividing. We named this protein "X"; it has a molecular weight of about 50000. A role was sought for the protein made throughout the cycle but showing its effect only at the end, Earlier observations by Dr Helene Smith showed that brief heating of the bacteria, (16 min at 45 °C) produced synchronous cell division; heating delayed division in a way suggesting that a protein needed for division had been damaged and must be resynthesized before division occurs. Damage to this protein causes the celis to swell; this swelling appears to be the prime basis far the delay of cell division, as shown recently by Dr Po Chi Wu. The swelling caused by an osmotic shift similarly delayed cell division; a result that is support for this hypothesis. A model is proposed for the role of the X protein as a sort af "girdle" that must be built up during the cycle, and that constricts the cells at the time of division. [ABSTRACT FROM AUTHOR]

A method is presented to isolate in pure form two acidic proteins, indicated as A1- and A2-protein from 50-S ribosomes of Escherichia coli. The advantage of this method is that it does not require prior isolation of subunits. The molecular weight of A1- and A2-protein was found by dodecylsulfate gel electrophoresis to be 11 500 with a maxum uncertainty of 1500. Sedimentation equilibrium centrifugation in 5 M guanidine hydrochloride indicates a molecular weight in the range of 12 000-13 000. The amino acid composition of the two proteins is remarkable and indistinguishable. A-protein has a high content of alanine and does not contain tyrosine, tryptophan, histidine or cysteine. On gel-electrofocusing the isoelectric points of A1- and A2-protein are slightly different, namely pH 4.7 and pH 4.85. The amount of A-protein in actively diving cells indicates that contrary to 30-S ribosomes, 50-S ribosomes have a restricted element of repeat. The number of copies of A-protein is found to be somewhat larger than two. [ABSTRACT FROM AUTHOR]

Fingerprints of tryptic digests of phenylalanyl-tRNA synthetase of Escherichia coli NP 3 suggest that the smallest identical subunit is one fourth of the size of the native protein (mol. wt 181000). Determination of the subunit size by gel electrophoresis reveals a molecular weight of 43000 = 2000. By the criteria employed the enzyme therefore seems to be composed of four identical subunits. Phenylalanyl-tRNA synthetase which has been denatured by treatment with 8M urea is able to reform active enzyme indistinguishable by its size from the native protein. Again, a size of about 45000 was determined for the subunits active in the association reaction. [ABSTRACT FROM AUTHOR]

Poly U-directed stimulation of preincubated calf lens ribosomes revealed that these particles from a mammalian source have a phenylalanine incorporation ability comparable to the Escherichia coli system. A search was made for optimal conditions. After variation of the magnesium concentration during preincubation two levels of maximal incorporation were observed. The region of highest relative stimulation did not coincide with these maxima. Preincubation under conditions of optimal amino acid incorporation yields 80S monomers and to a lesser extent 120S particles. No smaller units or breakdown products were observed in the analytical ultracentrifuge. Such particles could be demonstrated after prolonged dialysis of either polysomes or 80S monomers against 0.1 mM MgC12. Their sedimentation coefficients were 50S and 30S respectively but not 60 and 40 S. [ABSTRACT FROM AUTHOR]