An overview of some mechanisms of bacterial pathogenesis

The adherence of microorganisms to host surfaces is highly specific, and in many cases, essential for subsequent pathogenetic events to occur. A dynamic process leading to increased mucosal adherence of gram-negative bacilli to epithelial cell receptors in the oral cavity appears to be the initial step in the development of pneumonia. In infectious processes secondary to Streptococcus pneumoniae, adherence may also play a role in specific syndromes. In many cases, however, colonization of oropharyngeal mucus itself, the presence of capsular polysaccharide, and the release of various cell wall components appear to interact to cause clinical disease. In Neisseria gonorrhoeae infections, adherence is all important and is mediated by a number of cell surface structures. These have been studied extensively. Many of these structures, such as pili and protein II, exhibit great variability both between strains and in the same organism at different stages of infection. Others, such as protein I, are more constant. This information has been used in the production of specific vaccines to more preserved structures to inhibit adherence. These will be tested in the near future. It is our view that a better understanding of the many forms of bacterial adherence will be the key to our designing more effective strategies to detect early infection and to intervene more decisively to limit its spread.     

Location of the isoleucine arrest point in CHO and 3T3 cells

An isoleucine arrest point in G1 was determined by two methods for CHO and 3T3 cells. In the first method the fraction of cells entering S after isoleucine deprivation was assessed by [³H]thymidine labelling and autoradiography. In the second method cells entering S after isoleucine deprivation were identified by double-label autoradiography using [³H] and [¹⁴C]thymidine. From the fraction of cells entering S, determined by the two methods, the arrest point in G1 (and entry into G0) is located within the last 40 min of G1.     

Prediction of sequential antigenic regions in proteins

Prediction of antigenic regions in a protein will be helpful for a rational approach to the synthesis of peptides which may elicit antibodies reactive with the intact protein. Earlier methods are based on the assumption that antigenic regions are primarily hydrophilic regions at the surface of the protein molecule. The method presented here is based on the amino acid composition of known antigenic regions in 20 proteins which is compared with that of 314 proteins [(1978) Atlas of Protein Sequence and Structure, vol. 5, suppl. 3, 363-373]. Antigenicity values were derived from the differences between the two data sets. The method was applied to bovine ribonuclease, the B-subunit of cholera toxin and herpes simplex virus type 1 glycoprotein D. There was a good correlation between the predicted regions and previously determined antigenic regions.     

Role of the modulator protein in the interconversion of rabbit skeletal muscle protein phosphatase

The major active protein phosphatase present in a rabbit skeletal muscle extract is associated with the glycogen particle and migrates in sucrose density gradient centrifugation as a Mr = 70,000 protein and contains modulator activity. Addition of extra modulator protein causes a time- and concentration-dependent conversion of the enzyme to an inactive FA-ATP, Mg-dependent form. The intrinsic modulator in the active phosphatase is destroyed by limited proteolysis without an appreciable change in the phosphatase activity. The proteolyzed active enzyme has a lower molecular weight (Mr = 40,000) and it reassociates with the modulator producing a FA-ATP, Mg-dependent enzyme form (Mr = 60,000). The modulator protein is used stoichiometrically in the activation of the ATP, Mg-dependent phosphatase. This is in agreement with the presence of one unit of modulator activity per unit of native spontaneously active phosphatase.