When stimulated with antigen, B cells are influenced by T cells to proliferate and differentiate into antibody-forming cells. Since it was reported that soluble factors could replace certain functions of helper T cells in the antibody response, several different kinds of lymphokines and monokines have been reported in B-cell growth and differentiation. Among these, human B-cell differentiation factor (BCDF or BSF-2) has been shown to induce the final maturation of B cells into immunoglobulin-secreting cells. BSF-2 was purified to homogeneity and its partial NH2-terminal amino-acid sequence was determined. These studies indicated that BSF-2 is functionally and structurally unlike other known proteins. Here, we report the molecular cloning, structural analysis and functional expression of the cDNA encoding human BSF-2. The primary sequence of BSF-2 deduced from the cDNA reveals that BSF-2 is a novel interleukin consisting of 184 amino acids.

A cDNA coding for human interleukin-2 (IL-2) has been cloned from a cDNA library prepared from partially purified IL-2 mRNA. The DNA sequence codes for a polypeptide which consists of 153 amino acids including a putative signal sequence. A biologically active polypeptide, characteristic of human IL-2, was produced when the cDNA was fused to a simian virus 40 promoter sequence and used to transfect cultured monkey COS cells.

The crystal structure of a microbial transglutaminase from Streptoverticillium mobaraense has been determined at 2.4 Å resolution. The protein folds into a platelike shape, and has one deep cleft at the edge of the molecule. Its overall structure is completely different from that of the factor XIII-like transglutaminase, which possesses a cysteine protease-like catalytic triad. superimpose well on the catalytic triad "Cys-HisAsp" of the factor XIII-like transglutaminase, in this order. The secondary structure frameworks around these residues are also similar to each other. These results imply that both transglutaminases are related by convergent evolution; however, the microbial transglutaminase has developed a novel catalytic mechanism specialized for the cross-linking reaction. The structure accounts well for the catalytic mechanism, in which Asp 255 is considered to be enzymatically essential, as well as for the causes of the higher reaction rate, the broader substrate specificity, and the lower deamidation activity of this enzyme.Transglutaminase (TGase 1 ; protein-glutamine ␥-glutamyltransferase, EC 2.3.2.13) catalyzes an acyl transfer reaction in which the ␥-carboxyamide groups of peptide-bound glutamine residues act as the acyl donors. The most common acyl acceptors of TGase are the ⑀-amino groups of lysine residues within peptides or the primary amino groups of some naturally occurring polyamines (1, 2). When lysine residues in proteins serve as acyl acceptors, intermolecular or intramolecular ⑀-(␥-glutamyl)lysine bonds are formed, resulting in the polymerization of proteins.TGases are widely distributed in various organisms, including vertebrates (3-7), invertebrates (8, 9), mollusks (10), plants (11), and microorganisms (12). Among these TGases, the human blood coagulation factor XIII has been most characterized (13)(14)(15)(16)(17)(18). By catalyzing the cross-linking between fibrin molecules, factor XIII forms fibrin clots for hemostasis and heals a wound. The crystal structure of human factor XIII has been determined, revealing that it consists of four domains with a cysteine protease-like active site (19 -22). Many TGases are homologous to human factor XIII and share the common feature of Ca 2ϩ -dependent catalytic activity (3-8). A tissue-type TGase from red sea bream liver (fish-derived TGase (FTG)) is an example of such factor XIII-like TGases and shows 33% sequence homology to human factor XIII (7). The crystal structure of FTG has also been determined (23). The overall and active site structures of FTG are essentially similar to those of human factor XIII.A microbial TGase (MTG) has been isolated from the culture medium of Streptoverticillium sp. S-8112 (24), which has been identified as a variant of Sv. mobaraense. This enzyme is the first TGase obtained from a nonmammalian source. Thus far, few TGases have been identified from microorganisms, particularly from Streptoverticillium species (25). Although the physiological role of MTG is still unknown, this protein is secreted from the cytoplas...

Most strains of Pseudomonas aeruginosa produce various types of bacteriocins (pyocins), namely, R-, F-, and S-type pyocins. The production of all types of pyocins was shown to be regulated by positive (prtN) and negative (prtR) regulatory genes. The prtN gene activates the expression of various pyocin genes, probably by the interaction of its product with the DNA sequences conserved in the 5' noncoding regions of the pyocin genes. The prtR gene represses the expression of the prtN gene, and its product, predicted from the nucleotide sequence, has a structure characteristic of phage repressors and seems to be inactivated by the RecA protein activated by DNA damage. A model for the regulation of the pyocin genes is proposed.