Modifiable chromatophore proteins in photosynthetic bacteria

Analysis of QpRS-specific sequences from Coxiella burnetii

Coxiella burnetii from acute cases of Q fever possess a plasmid termed QpH1. Chronic isolates contain a plasmid termed QpRS or have QpRS sequences integrated into the chromosome. The correlation between an isolate's plasmid type and the chronic or acute nature of the disease has prompted analysis of unique plasmid sequences to determine if they contain virulence genes. DNA hybridization has determined that a portion of a 3.6-kb EcoR I fragment (epsilon') is unique to QpRS. In vitro transcription/translation (IVTT) of the epsilon' fragment yielded a 55-kDa protein regardless of the cloning orientation, suggesting that transcription resulted from a rickettsial promoter. A translational start site was mapped to the 1.2-kb Pst I-EcoR I subfragment of epsilon' by IVTT. DNA sequencing showed an open reading frame (ORF) of 1485 bp, capable of coding for a protein of ca. 55.9 kDa. This ORF was termed cbbE'. Putative promoter regions of cbbE' included TTTAAT (-35), TATAAT (-10), and a ribosome-binding site GGAGAGA. The ORF ended with a stop codon UAA and was followed by UAG and a potential factor-independent transcription-termination region. In-frame cloning of the 695-bp Pst I subfragment into pUC9 resulted in a fusion protein of ca. 37 kDa, confirming the frame and length of the ORF as predicted by DNA sequencing. The specificity of this gene to QpRS was confirmed by probing DNA from three plasmid groups of C. burnetii, using the internal 695-bp Pst I fragment of cbbE'.

Outer membrane protein mediating iron uptake via pyoverdinpss, the fluorescent siderophore produced by Pseudomonas syringae pv. syringae

In an iron-limited environment Pseudomonas syringae pv. syringae B301D produces a yellow-green fluorescent siderophore called pyoverdinpss which functions in high-affinity iron transport. Two-dimensional electrophoretic comparisons of the outer membrane proteins of strain B301D identified nine proteins which were expressed at low (50 nM) but not at high (10 microM) iron concentrations. Except for the minor protein 8e, the iron-regulated proteins exhibited high molecular weights ranging from approximately 74,000 to 80,000. A mutant of strain B301D incapable of iron uptake (Iu-) from ferric pyoverdinpss lacked the 74,000-molecular-weight protein 4a, which was the major iron-regulated outer membrane protein. In contrast, a nonfluorescent mutant (Flu-) unable to synthesize pyoverdinpss showed no quantitative or qualitative difference in its outer membrane profile from that of the wild-type strain. In plant pathogenicity tests the Iu- and Flu- strains caused typical brown necrotic and sunken lesions in immature sweet cherry fruit which were indistinguishable from those of the wild-type strain. Thus, excretion of pyoverdinpss and subsequent Fe(III) uptake do not have a determinative role in the pathogenicity or virulence of P. syringae pv. syringae.

A bacterial-induced lectin which triggers hemocyte coagulation in Manduca sexta

An inducible hemagglutinin termed M13, was purified from M. sexta hemolymph. M13 is a glucose-specific lectin which in addition to erythrocyte agglutination, can activate dedifferentiation of various hemocytes into a filamentous coagulation network. When lectin activity was inhibited with glucose or antiserum, neither erythrocyte agglutination or hemocyte coagulation occurred. When M13 was boiled or trypsin treated, hemocyte activation was lost, but erythrocyte agglutination remained. Hence M13 activity appears to be bimodal, possessing both a lectin activity and a hemocyte-coagulating activity.

Antibacterial hemolymph proteins of Manduca sexta

Exclusion column fractionated immune hemolymph of the M. sexta larva contains five peaks of anti-E. coli activity with molecular weights of greater than 140 kD and approximately 91, 54, 14 and 4 kD, plus one peak of lysozyme activity with a molecular weight of 17 kD. Purification of the 54 kD peak showed that this peak consists of the previously described M18 proteins which have monomeric weights of approximately 20 kD and had antibacterial activity against certain gram negative bacteria. Approximately 80% of the total hemolymph antibacterial activity was detected in the 14 and 4 kD peaks. These proteins, which kill both gram negative and gram positive bacteria, appeared to be directly analogous to the cecropins of H. cecropia. The greater than 140 and 91 kD peaks constituted only a minor part of the total antibacterial activity.

Membrane proteins correlated with expression of the polysialic acid capsule in Escherichia coli K1

Growth of Escherichia coli K1 strains at 15 degrees C results in a defect in the synthesis or assembly of the K1 polysialic acid capsule. Synthesis is reactivated in cells grown at 15 degrees C after upshift to 37 degrees C, and activation requires protein synthesis (Whitfield et al., J. Bacteriol. 159:321-328, 1984). Using this temperature-induced defect, we determined the molecular weights and locations of membrane proteins correlated with the expression of K1 (polysialosyl) capsular antigen. Pulse-labeling experiments demonstrated the presence of 11 proteins whose synthesis was correlated with capsule appearance at the cell surface. Using the differential solubility of inner and outer membranes in the detergent Sarkosyl, we localized five of the proteins in the outer membrane and four in the inner membrane. The subcellular location of two of the proteins was not determined. Five proteins appeared in the membrane simultaneously with the initial expression of the K1 capsule at the cell surface. One of these proteins, a 40,000-dalton protein localized in the outer membrane, was identified as porin protein K, which previously has been shown to be present in the outer membrane of encapsulated E. coli. The possible role of these proteins in the synthesis of the polysialosyl capsule is discussed.

N-terminal sequences of subunits L and M of the photosynthetic reaction centre from Rhodospirillum rubrum G-9+. Separation of the subunits by gel filtration on hydroxypropylated Sephadex G 100 in organic solvents

A new method has been developed by which subunits L and M of the photosynthetic reaction centre from Rhodospirillum rubrum G-9+ can be obtained in pure form, starting form freeze-dried chromatophore membranes. The method employs extraction into a mixture of chloroform/methanol and gel permeation chromatography on a column of hydroxypropylated Sephadex G 100. Cross-contamination of the purified subunits was less than 5% (mol/mol), as estimated by manual Edman degradation. Automated Edman degradation has been carried out with both subunits in a liquid-phase sequencer. 36 amino-acid residues of subunit L and 50 residues of subunit M could be unequivocally identified. In both cases, the sequence analyses came to a premature end as the signal sudden by dropped to the level of the accidental fluctuations of the phenylthiohydantoin-derivatives background. This effect is explained by the unusual susceptibility to peptide bond cleavage of certain threonine residues which probably underwent N leads to O acyl shift during the cleavage reactions. The N-terminal sequences have been compared to those of subunits L and M of the photosynthetic reactions centre from Rhodopseudomonas sphaeroides R-26 (sutton, M.R., Rosen, D., Feher, G. & Steiner, L.A. (1982) Biochemistry 21, 3842-3849). The homology among subunits L is close to 90% and thus markedly higher than that among subunits M (32%). This finding indicates a pre-eminent role of subunit L in the primary events of photosynthetic energy conversion.

Extraction of detergents from hydrophobic proteins with isopentanol: application to electrophoretic analysis of photosynthetic bacterial hydrophobic proteins

The method for extracting Triton X-100 used by I. H. Mather and C. B. Tampling [Anal. Biochem. 93, 139-142 (1979)], has been extended to other detergents of different charge and chemical nature. All the detergents tested can be extracted with isopentanol in conditions in which not more than 8% of hydrophobic or hydrophilic protein is lost from the water phase. The removal of detergent from reaction centers and light harvesting protein-pigment complexes of photosynthetic bacteria, eliminates the artifacts of oligomers when analyzed by sodium dodecyl sulfate-gel electrophoresis.

Outer membrane protein composition of Yersinia pestis at different growth stages and incubation temperatures

The protein composition of the outer membrane of Yersinia pestis grown at 26 and at 37 degrees C was examined. The outer membrane was isolated by isopycnic sucrose density centrifugation, and its degree of purity was determined with known inner and outer membrane components. Using two-dimensional gel electrophoresis, we identified a large number of heat-modifiable proteins in the outer membrane of cells grown at either incubation temperature. One-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis of heated preparations indicated five proteins in the outer membrane of 37 degrees C-grown cells not evident in 26 degrees C-grown cells. Differences in the protein composition of the outer membrane due to the stage of growth were evident at both 26 degrees C and 37 degrees C, although different changes were found at each temperature. When cell envelopes were examined for the presence of peptidoglycan-associated proteins, no differences were seen as a result of stage of growth. Envelopes from 26 degrees C-grown cells yielded two peptidoglycan-associated proteins, E and J. Cells grown at 37 degrees C, however, also contained an additional protein (F) which was not found in either the bound or free form 26 degrees C. The changes in outer membrane protein composition in response to incubation temperature may relate to known nutritional and antigenic changes which occur under the same conditions.

Isolation and partial characterization of the major outer membrane protein of Chromatium vinosum

The 42,000 major outer membrane protein of Chromatium vinosum was purified by a combination on ion-exchange chromatography, gel filtration, and isoelectric focusing. Upon isoelectric focusing, the final material produced four major hands. Three of the four bands were isolated and analyzed for similarity or differences. Protease peptide maps and cyanogen bromide maps of the three isoelectric species were identical. When the isolated isoelectric species were refocused, each produced multiple isoelectric species, suggesting that the procedure used was generating the multiple charged species. Protease treatment of the isolated outer membrane produced a 31,000 fragment from the 42,000 protein. This fragment was isolated by preparative sodium sulfate-polyacrylamide gel electrophoresis. Although the amino acid compositions of the 42,000 protein and its 31,000 trypsin fragment were different, their polarity index was the same (45%). The amino-terminal sequences of the 42,000 protein and 31,000 trypsin fragment were identical, and it concluded that the amino-terminal was buried in the membrane.

Characterization of the cell wall and cell wall proteins of Chromatium vinosum

Highly purified cell walls of Chromatium vinosum were isolated by differential centrifugation, with or without Triton X-100 extraction. The isolated material had a protein composition similar to that of cell walls obtained by sucrose density gradient centrifugation. Twenty-two proteins were reproducibly detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A 42-kilodalton protein was shown to account for 65% of the total cell wall protein. The majority of cell wall proteins were solubilized in sodium dodecyl sulfate at room temperature; however, they existed as high-molecular-weight complexes unless heated to 45 degrees C or above. The cell wall contained one heat-modifiable protein which migrated with an apparent molecular weight of 37,400 when solubilized at 70 degrees C or below, but which migrated with an apparent molecular weight of 52,500 if solubilized at 100 degrees C. The electrophoretic mobility of three proteins was modified by 2-mercaptoethanol. The majority of C. vinosum cell wall proteins had isoelectric points between pH 4.5 and 5.5, and the 42-kilodalton protein focused at pH 4.9. No proteins were detected which were analogous to the lipoprotein or peptidoglycan-associated proteins of the Enterobacteriaceae. Nearest-neighbor analysis with a reducible, cross-linking reagent indicated that three proteins, including the 42-kilodalton protein, associated with themselves. Most of the cell wall proteins were partially accessible to proteases in both intact cells and isolated cell walls. Protease treatment of the whole cell or isolated cell wall digested approximately an 11,000-molecular-weight portion of the 42-kilodalton protein.