摘要:

AbstractFull‐length tissue‐type plasminogen activator (t‐PA) cDNA served to construct deletion mutants within the N‐terminal “heavy” (H)‐chain of the t‐PA molecule. The H‐chain cDNA consists of an array of structural domains homologous to domains present on other plasma proteins (“finger,” “epidermal growth factor,” “kringles”). These structural domains have been located on an exon or a set of exons. The endpoints of the deletions nearly coincide with exon‐intron junctions of the chromosomal t‐PA gene. Recombinant t‐PA deletion mutant proteins were obtained after transient expression in mouse Ltk−, cells, transfected with SV40‐pBR322‐derived t‐PA cDNA plasmids. It is demonstrated that the serine protease moiety of t‐PA and its substrate specificity for plasminogen is entirely contained within the C‐terminal “light” (L)‐chain of the protein. The presence of cDNA, encoding the t‐PA signal peptide preceding the remaining portion of t‐PA, suffices to achieve secretion of (mutant) t‐PA into the medium. The stimulatory effect of fibrin on the plasminogen activator activity of t‐PA was shown to be mediated by the kringle K2 domain and, to a lesser extent, by the finger domain. The other domains on the H‐chain, kringle Kl, and the epidermal growth‐factor‐like domain, do not contribute to this property of t‐PA. These findings correlate well with the fibrin‐binding properties of the rt‐PA deletion‐mutant proteins, indicating that stimulation of the activity is based on aligning of the substrate plasminogen and its enzyme t‐PA on the fibrin matrix. The primary target for endothelial plasminogen activator inhibitor (PAI) is located within the L‐chain of t‐PA. Deleting specific segments of t‐PA H‐chain cDNA and subsequent transient expression in mouse Ltk−cells of t‐PA deletion‐m

ISSN:0730-2312    

DOI:10.1002/jcb.240320302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractMany human cells and cell lines possess a specific receptor that binds urokinase plasminogen activator (uPA) with an affinity of about 10−10M. Bound enzyme is not internalized, is slowly dissociated, and retains its enzymatic activity. The amino acid sequence of uPA responsible for receptor binding is located within the first 35 aminoterminal residues, ie, in the growth factor domain. Binding, however, is not competed for by other proteins that contain the growth factor domain (including epidermal growth factor). Cells that produce uPA secrete the pro‐uPA form, which subsequently binds to the receptor. A431 cells, in fact, have their receptors completely saturated with pro‐uPA. It is proposed that uPA:uPA‐receptor interaction plays a direct role in physiological and pathological processes that require cell mi

ISSN:0730-2312    

DOI:10.1002/jcb.240320303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

ISSN:0730-2312    

DOI:10.1002/jcb.240320304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractSignal peptidase has been purified approximately 600‐fold from hen oviduct microsomes. Treatment of microsomes with ice‐cold sodium carbonate at pH 11.5 removes soluble and extrinsic membrane proteins prior to solubilization of signal peptidase with Nonidet P‐40. After dialysis to pH 8.2, the solubilized enzyme is chromatographed on diethylaminoethyl cellulose at pH 8.2. More than 90% of contaminating proteins bind to the column while signal peptidase and endogenous phospholipid are eluted in the column void volume. Enzyme activity subsequently binds to carboxymethyl cellulose at pH 5.8 and is eluted by approximately 100 to 200 mM NaCl during a NaCl gradient. Polypeptides present in partially purified hen oviduct signal peptidase have relative molecular masses ranging from 54 kD to less than 11 kD with major bands at 29, 23, 22, 19, 18 and 13 kD. The purified peptidase requires phospholipid for activity and is maximally active in the presence of 2 mg/ml phosphatidylch

ISSN:0730-2312    

DOI:10.1002/jcb.240320305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractWe have recently described a platelet factor that is similar to the fibroblast thrombin inhibitor protease nexin I (PNI) [12]. The present manuscript shows that this platelet form of PN (PNp) does not complex [125I]‐thrombin that has been blocked at its active site, consistent with the conclusion that it is a thrombin inhibitor. When platelets are incubated with [125I]‐thrombin, PNp‐[125MI]‐thrombin complexers accumulate both in the medium and on the platelet surface. In the case of fibroblasts, PNI‐[125I]‐thrombin Complexes that form in solution bind to the cells as a consequence of a receptor‐mediated clearance process [Low et al, Proc Natl Acad Sci USA 78:2340, 1981]. We show here that the PNp‐[125I]‐thrombin complexes that accumulate in platelet‐binding incubation medium do not bind to platelets. Thus, the platelet‐associated complexes must form by [125I]‐thrombin binding to PNpthat is associated with the platelet surface. Pretreatment of platelets with heparin markedly increases the number of PNp‐[125I]‐thrombin complexes that form on platelets. The basis for this increase in unclear. This effect seems incompatible with a heparinlike factor acting as the s

ISSN:0730-2312    

DOI:10.1002/jcb.240320306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractActivated ras transforming genes have been described in a variety of neoplasms and encode 21,000‐Dalton (p21) proteins with amino acid substitutions at positions 12, 13, and 61. In this report we describe a monoclonal antibody designated DWP that reacts. Specifically with synthetic dodecapeptides containing valine at position 12, to a lesser extent with peptides containing cysteine at position 12 and not with peptides containing glycine, arginine, serine, aspartic acid, glutamic acid or alanine at the same position. Western blot and immunoperoxidase studies showed that DWP specifically reacts with activated rasHor rasKproteins in NIH cells transformed by DNA from the human carcinoma cells that encode valine at position 12. DWP did not react with normal p21s encoding glycine at position 12, nor with activated p21s encoding aspartic acid, glutamic acid, arginine, serine, or cysteine at position 12. A survey of human tumor cell lines demonstrated that DWP reacted with the human bladder carcinoma cell line T24 but not with human tumor cell lines previously shown td contain other activating mutations at positions 12 or 61. DWP and perhaps additional antibodies that specifically react with alterations at positions 12 or 61 of the ras protein may be valuable in determining the presence and frequency of activated ras proteins in human malignanc

ISSN:0730-2312    

DOI:10.1002/jcb.240320307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractA heritable mutation predisposes an individual to certain childhood malignancies, such as retinoblastoma and Wilms' tumor. The chromosomal locations of the genes responsible for the predisposition are known by linkage with chromosomal deletions and enzyme markers. A study of these tumors in comparison to the normal constitutional cells of the patients, using enzyme and DNA markers near the predisposing genes, has shown that these genes are recessive to normal wild‐type alleles at the cellular level. Expression of the recessive phenotype (malignancy) involves the same genetic events that were observed in Chinese hamster cell hybrids carrying recessive drug resistance genes. In both the experimental and clinical situations, the wild‐type allele is‐most commonly eliminated by chromosome loss with duplication of the mutant chromosome. Simple chromosome loss and mitotic recombination have been documented in both systems. In the remaining 30% of cases, inactivation or microdeletion of the wild‐type allele are assumed to be responsible for expression of the recessive phenotype. Osteo‐sarcoma is a common second tumor in patients who have had retinoblastoma. Studies with markers in osteosarcoma show that these tumors also result from unmasking of the recessive phenotype by loss of the normal allele at the retinoblastoma locus, whether or not the patient had retinoblastoma. Subsequent chromosomal rearrangements and amplification of oncogenes that occur in these homozygous tumors provide progressive growth advantage. In other malignancies, in which studies have so far focused on oncogene amplification and chromosomal rearrangements, unmasking of recessive mutations may also be the critical initiati

ISSN:0730-2312    

DOI:10.1002/jcb.240320308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractA procedure for the simultaneous extraction and purification of four calcimedins from chicken gizzard, rat liver, and bovine liver is described. These proteins bind to hydrophobic resins in a calcium‐dependent manner similar to calmodulin and troponin C. The four calcimedins purified had molecular weights 67,000 (67K), 35,000 (35K), 33,000 (33K), and 30,000 (30K) as determined by SDS polyacrylamide gel electrophoresis. Their ability to bind calcium was demonstrated using the Hummel‐Dreyer method. Their tissue concentration ranged between 1–4 mg/ 100 g wet weight in the three tissues studied. During gel filtration, calcimedins 67K and 35K, had Rf (Ve‐Vo/Vt‐Vo) values of 0.46 and 0.74, respectively, indicating monomeric structure. However, the 33K and 30K calcimedins had Rf values of 0.26 (molecular weights>90,000) suggesting that they occur as subunit complexes in their native state. Antibodies raised against the 67K and 35K calcimedins showed cross reactivity suggesting possible common origin. However, peptide mapping studies showed that they are independent proteins with considerable peptide homology. Antibodies to 30/33K calcimedins did not cross‐react with either 67K or 35K calcimedins. Moreover, their peptide maps were strikingly different from those of 67K and 35K calcimedins indicating that they are unique. At present, the regulatory function of this group of proteins is not clear. Indirect evidences support the possibility that they are involved in membrane associated events, such as endocytosis an

ISSN:0730-2312    

DOI:10.1002/jcb.240320309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

摘要:

AbstractIn the rat hepatoctye, the internalization and degradation of asialoglycoproteins and the secretion of plasma and biliary proteins require specific intracellular sorting of vesicles. To aid in the biochemical characterization of these different vesicular pathways, we examined the effects of the ionophore monensin on the uptake and degradation of125I‐asialoorosomucoid (ASOR) and on the secretion of plasma and biliary proteins by the in situ perfused rat liver. In control livers, 77% of injected125I‐ASOR was extracted on first pass; 93% of the extracted radioactivity was released back into the circulation (totally degraded and some intact ASOR was found); and approximately 2% was recovered in the bile, some of which was intact. Monensin treatment decreased first pass uptake of125I‐ASOR to 57% and abruptly blocked the release of radioactivity into the perfusate and the bile. When hepatic proteins were biosynthetically labeled with3H‐leucine, monensin treatment dramatically reduced and delayed the secretion of newly synthesized proteins into both the perfusate and the bile. In contrast with control livers, in which secretion of protein into the perfusate preceded secretion of protein into the bile, TCA‐precipitable3H‐protein appeared in bile about 20 min before TCA‐precipitable3H‐protein appeared in the perfusate in monensin‐treated livers. Thus, monensin treatment in the perfused liver blocked the degradation of asialoglycoproteins and inhibited the secretion of plasma proteins but had less effect on biliary protein secretion. These data document physiologic effects of monensin in an intact organ and suggest that biochemical distinctions between different vesicular pathways exist in t

ISSN:0730-2312    

DOI:10.1002/jcb.240320310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY

ISSN:0730-2312    

DOI:10.1002/jcb.240320301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1986

数据来源: WILEY