The noncatalytic domain of the human T cell protein tyrosine phosphatase (TCPTP) is alternatively spliced to generate a 45-kD form, p45TC, and a 48-kD form, p48TC (Champion-Arnaud et al., 1991; Mosinger et al., 1992). This manuscript concerns structural motifs in the noncatalytic segment of the enzyme responsible for targeting the two forms to different subcellular compartments. Endogenous and transiently expressed p48TC associates with the ER, as determined by sucrose gradient fractionation and indirect immunofluorescence, respectively. By contrast, p45TC localizes in the nucleus even though upon cell lysis it is not retained and fractionates with markers for soluble enzymes. Using fusion proteins consisting of beta-galactosidase and COOH-terminal fragments of p48TC, two motifs necessary for ER retention within a 70-residue targeting segment have been identified. These include the terminal 19 hydrophobic residues which comprise a potential membrane-spanning segment and residues 346-358 which encompass a cluster of basic amino acids that may represent another type of ER retention motif. The sequence RKRKR, which immediately precedes the splice junction, functions as a nuclear localization signal for p45TC.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAn aspartate residue in yeast alcohol dehydrogenase I determines the specificity for coenzymeFan Fan, James A. Lorenzen, and Bryce V. PlappCite this: Biochemistry 1991, 30, 26, 6397–6401Publication Date (Print):July 2, 1991Publication History Published online1 May 2002Published inissue 2 July 1991https://pubs.acs.org/doi/10.1021/bi00240a008https://doi.org/10.1021/bi00240a008research-articleACS PublicationsRequest reuse permissionsArticle Views442Altmetric-Citations63LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
Abstract The Drosophila PS1 and PS2 integrins are required to maintain the connection between the dorsal and ventral wing epithelia. If αPS subunits are inappropriately expressed during early pupariation, the epithelia separate, causing a wing blister. Two lines of evidence indicate that this apparent loss-of-function phenotype is not a dominant negative effect, but is due to inappropriate expression of functional integrins: wing blisters are not generated efficiently by misexpression of loss-of-function αPS2 subunits with mutations that inhibit ligand binding, and gain-of-function, hyperactivated mutant αPS2 proteins cause blistering at expression levels well below those required by wild-type proteins. A genetic screen for dominant suppressors of wing blisters generated null alleles of a gene named moleskin, which encodes the protein DIM-7. DIM-7, a Drosophila homolog of vertebrate importin-7, has recently been shown to bind the SHP-2 tyrosine phosphatase homolog Corkscrew and to be important in the nuclear translocation of activated D-ERK. Consistent with this latter finding, homozygous mutant clones of moleskin fail to grow in the wing. Genetic tests suggest that the moleskin suppression of wing blisters is not directly related to inhibition of D-ERK nuclear import. These data are discussed with respect to the possible regulation of integrin function by cytoplasmic ERK.
ABSTRACT The initiation of gene expression in response to Drosophila receptor tyrosine kinase signaling requires the nuclear import of the MAP kinase, D-ERK. However, the molecular details of D-ERK translocation are largely unknown. In this regard, we have identified D-Importin-7 (DIM-7), the Drosophila homolog of vertebrate importin 7, and its gene moleskin. DIM-7 exhibits a dynamic nuclear localization pattern that overlaps the spatial and temporal profile of nuclear, activated D-ERK. Co-immunoprecipitation experiments show that DIM-7 associates with phosphorylated D-ERK in Drosophila S2 cells. Furthermore, moleskin mutations enhance hypomorphic and suppress hypermorphic D-ERK mutant phenotypes. Deletion or mutation of moleskin dramatically reduces the nuclear localization of activated D-ERK. Directly linking DIM-7 to its nuclear import, this defect can be rescued by the expression of wild-type DIM-7. Mutations in the Drosophila Importin β homolog Ketel, also reduce the nuclear localization of activated D-ERK. Together, these data indicate that DIM-7 and Ketel are components of the nuclear import machinery for activated D-ERK.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPurification and characterization of a human recombinant T-cell protein-tyrosine-phosphatase from a baculovirus expression systemN. F. Zander, J. A. Lorenzen, D. E. Cool, N. K. Tonks, G. Daum, E. G. Krebs, and E. H. FischerCite this: Biochemistry 1991, 30, 28, 6964–6970Publication Date (Print):July 16, 1991Publication History Published online1 May 2002Published inissue 16 July 1991https://pubs.acs.org/doi/10.1021/bi00242a022https://doi.org/10.1021/bi00242a022research-articleACS PublicationsRequest reuse permissionsArticle Views131Altmetric-Citations49LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
5′‐ p ‐Fluorosulfonylbenzoyl adenosine (FSBA), an ATP‐like affinity labelling reagent, reacted with rabbit skeletal muscle myosin light chain kinase (skMLCK) and its calmodulin complex in a site‐specific manner. Reaction was dependent upon the presence of the adenosine moiety of FSBA, saturated with increasing FSBA, was inhibited by MgATP, and was accompanied by stoichiometric incorporation of [ 14 C]FSBA. The kinetic constants describing the reaction were similar for skMLCK and its calmodulin complex: k 3 = −0.040 min −1 and −0.038 min t‐1 , and K i =0.18 mM and 0.40 mM, respectively. It is concluded that the MgATP‐binding site on skMLCK remains accessible at all times and maintains a near constant conformation.
