Outer membrane vesicles (OMVs) of Gram-negative bacteria form an important aspect of bacterial physiology as they are involved in various functions essential for their survival. The OMVs of the Antarctic bacterium Pseudomonas syringae Lz4W were isolated, and the proteins and lipids they contain were identified. The matrix-assisted laser desorption/ionization time of flight (MALDI-TOF/TOF) analysis revealed that phosphatidylethanolamines and phosphatidylglycerols are the main lipid components. The proteins of these vesicles were identified by separating them by one-dimensional gel electrophoresis and liquid chromatography coupled to electrospray ionization tandem mass spectrometry (ESI-MS/MS). They are composed of outer membrane and periplasmic proteins according to the subcellular localization predictions by Psortb v.3 and Cello V2.5. The functional annotation and gene ontology of these proteins provided hints for various functions attributed to OMVs and suggested a potential mechanism to respond to the extracellular environmental changes. The OMVs were found to protect the producer organism against the membrane active antibiotics colistin and melittin but not from streptomycin. The 1-N-phenylnapthylamine (NPN)-uptake assay revealed that the OMVs protect the bacterium from membrane active antibiotics by scavenging them and also showed that membrane and protein packing of the OMVs was similar to the parent bacterium. The sequestering depends on the composition and organization of lipids and proteins in the OMVs.

Lactoferrin (Lf)t is an 80-kD iron-binding glycoprotein found in high concentrations in human milk and at much lower but detectable levels in a number of other secretions of glandular epithelium (1). The principal functions of Lf are thought to be iron transport and storage (2), and bacteriostasis through strong chelation of iron required for microbial growth (3). However, Lf is also a major constituent of the secondary or specific granules of neutrophils (4), and has been implicated in several operational and regulatory functions in the immune and hematopoietic systems (5). To date, only a single form of Lf has been described, and is presumed to account for all of the diverse functions of the molecule.One of us (M. R. Das) previously reported (6) the presence in human milk of a unique and potent RNase activity, termed human milk RNase (hmRNase). This enzyme was initially identified based on its interference with the detection ofretrovirallike RNAs in human milk, and was subsequently shown to be present in low concentrations in a consanguineous community with a high incidence of breast cancer, the Parsi women of Bombay. The hmRNase was detected in high concentrations only in human milk and was thus considered to be potentially a marker for breast epithelium as well as for risk to development of breast cancer.The hmRNase has recently been purified to homogeneity and revealed to be a high molecular mass (80 kD) glycoprotein with a preference for mRNAs, viral RNAs, and purine homopolymers (7). Activity of the enzyme is influenced by various cations and is optimal at pHs of 7.5-8 .0.We report here that hmRNase is an isoform of Lf, sharing physical, chemical, and antigenic properties with the major species of Lf, but differing from it in the possession of potent nuclease activity and in the lack of significant iron-binding capacity. These findings establish the presence of multiple forms of Lf, with very distinctive properties, that may be related to the highly diverse physiological functions of the molecule .

Outer membrane vesicles (OMVs) of gram-negative bacteria are released during all growth phases and play an important role in bacterial physiology. They consist of lipids, proteins, lipopolysaccharides and other molecules. The OMVs of the Antarctic bacterium Pseudomonas syringae Lz 4W were isolated and identified their proteins. The mass spectral data set deposited with PRIDE, accession number PXD 000221 is presented in this report. The proteins identified from the OMVs of P. syringae Lz4W, data of this study were published in the Journal of proteome research [1].

We have cloned and sequenced a tumor rejection antigen from a highly immunogenic rat histiocytoma, AK-5. Recombinant antigen induced an antibody response in syngeneic hosts, and the immunized animals showed significant resistance to AK-5 tumor challenge, where growth of the tumor was retarded. Autologous anti-AK-5 antibody, as well as the specific monoclonal antibodies raised against whole AK-5 cells, recognized the recombinant protein. Similarly, recombinant antigen was able to neutralize antitumor antibody in a complement-mediated lysis assay. Antibodies raised against the fusion protein recognized a 60-kDa protein from AK-5 cell extracts. A cDNA sequence analysis revealed significant homology with mouse thymus (81%), lymph node (83%), and human brain (71%) cDNAs; however, the function of these genes is not known. These observations suggest the recombinant protein to be a strong candidate for the tumor rejection antigen that is involved in the spontaneous regression of the AK-5 tumor in syngeneic hosts.

We showed earlier that the phosphorylation of a 38 kDa protein (~38) from rat liver plasma membrane is stimulated by rus or endogenous G-proteins. We have now estimated the level of expression of p38 in liver tissues from embryos at different stages of development, regenerating liver and also in tumor cell lines of hepatic origin. Our results indicate that the expression of p38 is negatively correlated with cell division. It is suggested that the phosphorylation of ~38, an event which is regulated by ras proteins and G-proteins, could be involved in signal transduction processes associated with the inhibitory regulation of cell division.