Comparison of model and nuclear magnetic resonance structures for the human inflammatory protein C5a

The model structure previously proposed for human C5a, based upon the crystal structure of the homologous protein human C3a, is compared to the solution structure of human C5a recently determined by nuclear magnetic resonance (NMR) methods in our laboratory. The general folding and helix topography of the C5a protein were modeled very well. The N-terminus, which is disordered in the C3a crystal, was correctly predicted in the C5a model both as to its being a helix and as to its docking site on the rest of the molecule. On the other hand, the NMR data show that the biologically important C-terminal residues are disordered in solution, unlike the model and the C3a crystal structure where this region was helical.     

Cloning and analysis of the spc ribosomal protein operon of Bacillus subtilis: comparison with the spc operon of Escherichia coli.

A segment of Bacillus subtilis chromosomal DNA homologous to the Escherichia coli spc ribosomal protein operon was isolated using cloned E. coli rplE (L5) DNA as a hybridization probe. DNA sequence analysis of the B. subtilis cloned DNA indicated a high degree of conservation of spc operon ribosomal protein genes between B. subtilis and E. coli. This fragment contains DNA homologous to the promoter-proximal region of the spc operon, including coding sequences for ribosomal proteins L14, L24, L5, S14, and part of S8; the organization of B. subtilis genes in this region is identical to that found in E. coli. A region homologous to the E. coli L16, L29 and S17 genes, the last genes of the S10 operon, was located upstream from the gene for L14, the first gene in the spc operon. Although the ribosomal protein coding sequences showed 40-60% amino acid identity with E. coli sequences, we failed to find sequences which would form a structure resembling the E. coli target site for the S8 translational repressor, located near the beginning of the L5 coding region in E. coli, in this region or elsewhere in the B. subtilis spc DNA.     

Induction of the chloramphenicol acetyltransferase gene cat-86 through the action of the ribosomal antibiotic amicetin: involvement of a Bacillus subtilis ribosomal component in cat induction.

The plasmid gene cat-86 and the cat gene resident on pC194 each encode chloramphenicol-inducible chloramphenicol acetyltransferase activity in Bacillus subtilis. Chloramphenicol induction has been proposed to result from chloramphenicol binding to ribosomes, which then permits the drug-modified ribosomes to perform events essential to induction. If this proposal were correct, B. subtilis mutants containing chloramphenicol-insensitive ribosomes should not permit chloramphenicol induction of either cat-86 or pC194 cat. However, we and others have been unable to isolate chloramphenicol-resistant ribosomal mutants of B. subtilis 168. We therefore developed a simple procedure for screening other antibiotics for the potential to induce cat-86 expression. One antibiotic, amicetin, was found to be an effective inducer of cat-86 but not of the cat gene on pC194. Amicetin and chloramphenicol each interact with the 50S ribosomal subunit, and the mechanism of cat-86 induction by both drugs may be similar. Amicetin-resistant mutants of B. subtilis were readily isolated, and in none of six mutants tested was cat-86 detectably inducible by amicetin, although the chloramphenicol-inducible phenotype was retained. The ami-1 mutation which is present in one of these amicetin-resistant mutants was mapped by PBS1 transduction to the "ribosomal gene cluster" adjacent to cysA. Additionally, ribosomes from cells harboring the ami-1 mutation contained an altered BL12a protein, as detected in two-dimensional polyacrylamide gel electrophoresis. Lastly, an in vitro protein-synthesizing system that uses ribosomes from an ami-1-containing cell line was more resistant to amicetin than a system that uses ribosomes from an amicetin-sensitive but otherwise isogenic strain. These results indicate that the host mutation, ami-1, which effectively abolished the inducibility of cat-86 by amicetin, altered a ribosomal component.     

A simple method for simultaneous estimation of zinc and copper in erythrocytes

A method is described for simultaneous estimation of zinc and copper in erythrocytes by hemolysis and flame aspiration atomic absorption spectrophotometry. Red blood cells (RBC) were also analyzed by the commonly used nitric acid digestion method for comparison. The difference in the results of zinc analyses of fifteen RBC samples by the two techniques was 0.5 ± 0.8 (mean ± SD) μg Zn/g hemoglobin indicating that these methods yield essentially similar results. Because of the low concentration of copper in RBC, results obtained by the acid digestion method were unreliable since nitric acid and undissolved particles of digested RBC in the acid extract increased instrumental noise to an unacceptable level. Average concentrations of zinc and copper estimated in RBC of 25 normal subjects by the present described technique (hemolysate method) were 43.9 and 2.0 μg/g Hb, respectively. No sex-related differences in RBC zinc or copper concentrations were found. The hemolysate method is simpler and faster to perform than the more commonly used nitric acid digestion method.     

Bacillus subtilis mutants with alterations in ribosomal protein S4.

Two mutants with different alterations in the electrophoretic mobility of ribosomal protein S4 were isolated as spore-plus revertants of a streptomycin-resistant, spore-minus strain of Bacillus subtilis. The mutations causing the S4 alterations, designated rpsD1 and rpsD2, were located between the argGH and aroG genes, at 263 degrees on the B. subtilis chromosome, distant from the major ribosomal protein gene cluster at 12 degrees. The mutant rpsD alleles were isolated by hybridization using a wild-type rpsD probe, and their DNA sequences were determined. The two mutants contained alterations at the same position within the S4-coding sequence, in a region containing a 12-bp tandem duplication; the rpsD1 allele corresponded to an additional copy of this repeated segment, resulting in the insertion of four amino acids, whereas the rpsD2 allele corresponded to deletion of one copy of this segment, resulting in the loss of four amino acids. The effects of these mutations, alone and in combination with streptomycin resistance mutations, on growth, sporulation, and streptomycin resistance were analyzed.     

Spectinomycin dependence in Bacillus subtilis.

Spectinomycin dependence in Bacillus subtilis involves two mutations, one conferring drug resistance and the other producing a requirement for spectinomycin for growth.