The amino acid sequence for chicken smooth muscle myosin light chain kinase (smMLCK) was deduced from a full-length cDNA. This has allowed dermition ofboth the complete sequence of the inactive 64-kDa proteolytic fragment, which contains the pseudosubstrate autoregulatory sequence, and of the active 61-kDa Ca2+/calmodulin-independent fragment, which lacks the autoregulatory domain. Comparison of the two sequences shows that the autoregulatory domain extends from Asn-780 to Arg-808. The peptide Leu-774 to Ser-787 does not inhibit smMLCK, whereas peptides of similar or shorter length from the pseudosubstrate region (Ser-787 to Val-807) are potent inhibitors. These data define the autoregulatory region as being contained within and probably identical to the pseudosubstrate domain. The catalytic and regulatory regions are flanked by several copies of 100-amino acid segments containing one of two consensus motifs. These motifs are absent from mammalian skeletal muscle MLCK or from Dictyostelium discoideum MLCK but are present in the Caenorhabditis elegans unc-22 gene product and the titin molecule of skeletal muscle myofibrils. These results indicate that the amino acid sequence of smMLCK encodes multiple functional motifs in addition to the catalytic domain.Myosin light chain kinases (MLCKs)

Escherichia coli strains are classified based on O-antigens that are components of the lipopolysaccharide (LPS) in the cell envelope. O-antigens are important virulence factors, targets of both the innate and adaptive immune system, and play a role in host-pathogen interactions. Because they are highly immunogenic and display antigenic specificity unique for each strain, O-antigens are the biomarkers for designating O-types. Immunologically, 185 O-serogroups and 11 OX-groups exist for classification. Conventional serotyping for O-typing entails agglutination reactions between the O-antigen and antisera generated against each O-group. The procedure is labor intensive, not always accurate, and exhibits equivocal results. In this report, we present the sequences of 71 O-antigen gene clusters (O-AGC) and a comparison of all 196 O- and OX-groups. Many of the designated O-types, applied for classification over several decades, exhibited similar nucleotide sequences of the O-AGCs and cross-reacted serologically. Some O-AGCs carried insertion sequences and others had only a few nucleotide differences between them. Thus, based on these findings, it is proposed that several of the E. coli O-groups may be merged. Knowledge of the O-AGC sequences facilitates the development of molecular diagnostic platforms that are rapid, accurate, and reliable that can replace conventional serotyping. Additionally, with the scientific knowledge presented, new frontiers in the discovery of biomarkers, understanding the roles of O-antigens in the innate and adaptive immune system and pathogenesis, the development of glycoconjugate vaccines, and other investigations, can be explored.

dVibrio tubiashii is reported to be a bacterial pathogen of larval Eastern oysters (Crassostrea virginica) and Pacific oysters (Crassostrea gigas) and has been associated with major hatchery crashes, causing shortages in seed oysters for commercial shellfish producers. Another bacterium, Vibrio coralliilyticus, a well-known coral pathogen, has recently been shown to elicit mortality in fish and shellfish. Several strains of V. coralliilyticus, such as ATCC 19105 and Pacific isolates RE22 and RE98, were misidentified as V. tubiashii until recently. We compared the mortalities caused by two V. tubiashii and four V. coralliilyticus strains in Eastern and Pacific oyster larvae. The 50% lethal dose (LD 50 ) of V. coralliilyticus in Eastern oysters (defined here as the dose required to kill 50% of the population in 6 days) ranged from 1.1 ؋ 10 4 to 3.0 ؋ 10 4 CFU/ml seawater; strains RE98 and RE22 were the most virulent. This study shows that V. coralliilyticus causes mortality in Eastern oyster larvae. Results for Pacific oysters were similar, with LD 50 s between 1.2 ؋ 10 4 and 4.0 ؋ 10 4 CFU/ml. Vibrio tubiashii ATCC 19106 and ATCC 19109 were highly infectious toward Eastern oyster larvae but were essentially nonpathogenic toward healthy Pacific oyster larvae at dosages of >1.1 ؋ 10 4 CFU/ml. These data, coupled with the fact that several isolates originally thought to be V. tubiashii are actually V. coralliilyticus, suggest that V. coralliilyticus has been a more significant pathogen for larval bivalve shellfish than V. tubiashii, particularly on the U.S. West Coast, contributing to substantial hatchery-associated morbidity and mortality in recent years. Another bacterium, Vibrio coralliilyticus, is best known as a coral pathogen responsible for coral bleaching and has been associated with significant losses to coral reefs worldwide (7,8). Recently, V. coralliilyticus was shown to be infectious to a variety of fish and shellfish, including Pacific oyster larvae (9, 10), the great scallop (Pecten maximus) and the European flat oyster (Ostrea edulis) (10), rainbow trout (Oncorhynchus mykiss), and larval brine shrimp (Artemia spp.) (11). Around the time that V. coralliilyticus was shown to be pathogenic to fish and shellfish, it was also learned through DNA sequencing that some marine isolates thought to be V. tubiashii were actually V. coralliilyticus (7,12). V. coralliilyticus and V. tubiashii are closely related phylogenetically (7, 13). Although some major hatchery crashes have been linked to V. tubiashii (3), it is now known that some of the etiological agents reported to be V. tubiashii are actually V. coralliilyticus. The strains formerly known as Vibrio tubiashii ATCC 19105, maintained by the American Type Culture Collection (ATCC, Manassas, VA), and V. tubiashii RE22, isolated from Pacific oyster larvae from a hatchery in Oregon (3), have been shown by sequencing to be V. coralliilyticus strains (12). Whole-genome sequencing was recently completed on RE98 (22), which was previously identified as a highly pat...