A protein phosphatase was cloned that interacts with a serine-threonine receptor-like kinase, RLK5, from Arabidopsis thaliana. The phosphatase, designated KAPP (kinase-associated protein phosphatase), is composed of three domains: an amino-terminal signal anchor, a kinase interaction (KI) domain, and a type 2C protein phosphatase catalytic region. Association of RLK5 with the KI domain is dependent on phosphorylation of RLK5 and can be abolished by dephosphorylation. KAPP may function as a signaling component in a pathway involving RLK5.

Clk/STY, the murine homologue of the recently described LAMMER family of protein kinases, autophosphorylates on serine/threonine and tyrosine residues in vitro and in vivo. LAMMER kinases are found throughout eukaryotes and possess virtually complete amino acid identity in many domains critical for kinase function, leading to the question of whether other family members also possess dual specificity. We report here that the Drosophila family member DOA, human SK-G1, and the Saccharomyces cerevisiae KNS1, all possess protein kinase activity and autophosphorylate with dual specificity in vitro, suggesting that the entire family possesses this activity. Although the LAMMER kinases are closely related to the mitogen-activated protein kinase family, they possess different substrate specificity in vitro, based on phosphorylation of peptide and protein substrates and sequencing of a phosphorylation site in a common substrate.Protein kinases are generally differentiated according to the specificity with which they phosphorylate substrates, with activity toward serine/threonine or tyrosine residues (1, 2). Recently, some kinases capable of phosphorylating all three amino acid residues have been identified (reviewed in Refs. 3 and 4). Such "dual specificity" kinases would be classified as serine/threonine-specific based on their amino acid sequences. Among these is murine STY or Clk (5, 6), whose cDNAs were isolated because their products autophosphorylated on tyrosine residues. Data base searches with the sequence of cDNAs from the Doa locus of Drosophila revealed murine Clk and other closely related homologues in eukaryotes ranging from yeast to humans (7). Additional homologues have subsequently been described in green plants (8) 1 (also accession number D49304 from the rice genome sequencing project), from rat (accession number X94351), and from Schizosaccharomyces pombe (accession number Z69239), a third family member in humans (9), a mink family member whose message is induced by cycloheximide in cultured cells (10), and a member from S. pombe, found in the genome sequencing project of this organism (accession number Z69239). We have dubbed these the LAMMER protein kinases, based upon the existence of this motif, or conserved variations upon it, in all members (7).The LAMMER kinases are nearly identical in size, spacing, and placement of their kinase catalytic domains and also show extremely high amino acid identity in domains essential for phosphotransfer to the peptide substrate and in substrate recognition (11). By analogy with the structure of two crystallized protein kinases (12, 13), the LAMMER motif lies in an ␣-helix below the substrate-binding cleft, potentially allowing it to make contact with substrates, and suggesting that these molecules are also highly conserved. Much of what is known of LAMMER kinase function derives from analysis of the Drosophila locus Doa, whose mutants were isolated during screens for loci with transcriptional regulatory effects (14,15). Doa is an essential gene; its mutations alt...

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We examined the role of Klebsiella fimbrial types 1 and 3 in mediating adherence to human buccal and tracheal cells and to lung tissue sections. We found that clinical isolates ofKlebsiella pneumoniae producing type 3 fimbriae and Escherichia coli HB101 containing a recombinant plasmid encoding expression ofKkebsiella type 3 fimbriae (pFKIO) demonstrated increased adherence to tracheal cells, trypsinized buccal cells, and lung tissue sections, in contrast to nonfimbriate and to type 1 fimbriate bacteria. Adherence by type 3 fimbriate bacteria was inhibited by purified type 3 fimbriae and Fab fragments derived from type 3 fimbrial-specific polyclonal immunoglobulin G. Type 3 fimbriae mediated attachment to the basolateral surface of tracheal cells and to the basal epithelial cells and the basement membrane regions of bronchial epithelia. Using an E. coli transformant (pDC17/pFK52), which expresses nonadherent P fimbrial filaments, along with the type 3 fimbrial adhesin (MrkD), we demonstrated that type 3 fimbrial attachment to respiratory cells was attributable to the MrkD adhesin subunit. Subsequent experiments demonstrated that the epithelial target of the type 3 fimbrial adhesin was most likely a peptide molecule rather than a carbohydrate. The results of this study demonstrate that, in vitro, the KlebsieUla type 3 fimbrial adhesin mediates adherence to human respiratory tissue.

We have employed fluorescein and 1251-labeled elicitors of the defense response in soybeans to monitor the cellular distribution and movement of elicitors following their addition to a soybean cell suspension culture. Our results indicate that the macromolecular elicitors first bind to the cell surface and then internalize in a temperature-and energy-dependent endocytotic process. Within a few hours, virtually all of the elicitor is concentrated in the major vacuole or tonoplast of the cell. Nonspecific (control) proteins neither bound to the cell surface nor internalized in parallel assays.