Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.22.32 (bromelain)
 1,025 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The site of bromelain cleavage in the haemagglutinin of the Hong Kong influenza virus A/Memphis/102/72 has been determined by using a diagonal peptide mapping procedure on the thermolytic digest of amidated BHA. The data show that bromelain cleavage removes the C-terminal 46 residues from HA2, and that the new carboxyl-terminal residue of BHA2 is Gly 175. This is close to the beginning of the hydrophobic membrane-interacting sequence that starts at residue 183.
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PMID:The location of the bromelain cleavage site in a Hong Kong influenza virus Haemagglutinin. 728 98

Hydrodynamic properties of hemagglutinin isolated with bromelain from influenza virus were studied. The sedimentation constant determined by the method of analytical ultracentrifugation was 9.17 +/- 0.17 S. The translation diffusion coefficient estimated by the method of optic mixing spectroscopy comprised (3.6 +/- 0.1) X 10(+7) cm2/s. A comination of both the constants in Svedberg's equation allowed calculation of the hemagglutinin molecular weight (approximately 230,000) which suggests a three-subunit structure of the molecule. The hydrodynamic diameter and friction ratio of an isolated molecule were calculated.
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PMID:[Influenza virus hemagglutinin: hydrodynamic properties and molecular weight]. 741 51

The hemagglutination (HA) and receptor destroying enzyme (RDE) activities of a newly isolated mouse enteric coronavirus (designated as DVIM) are described. DVIM agglutinates mouse or rat red blood cells (RBC) at 4 degrees C. At 37 degrees C the agglutination was rapidly reversed. The optimal pH for HA and for RDE activities using mouse red cells were shown to be 6.5 and 7.3 respectively. Hemagglutination by DVIM was not inhibited by pretreatment of RBCs with Vibrio cholerae filtrate or by pretreatment with Influenza-A neuraminidase. Therefore, the DVIM receptors on RBCs differ from the receptors of Influenza-A, and the RDE activity of DVIM acts specifically on this receptor. In addition, an analysis of the DVIM polypeptides showed that the virions contain five major, VP1 (M.W. 139,000), VP2 (68,000), VP3 (53,000), VP4 (38,000), VP5 (22,000) and two minor, VP1a (110,000), VP1b (100,000) polypeptides. VP1 and VP1b were digested by bromelain, suggesting that they constitute the surface glycoproteins.
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PMID:Hemagglutination and structural polypeptides of a new coronavirus associated with diarrhea in infant mice. 743 41

The tryptophan and tyrosine content of the bromelain-released subtype H3 haemagglutinin (H3 BHA) of influenza virus were measured by u.v. absorption and fluorescence techniques. The values obtained (8 and 18 residuces, respectively) are in close agreement with those derived from amino acid analysis. Essentially all of th tryptophan residues are demonstrated to be localized on the surface of the BHA molecule.
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PMID:Influenza virus haemagglutinin: estimation of tryptophan and tyrosine content and localization of tryptophan residues. 746 4

The complete amino acid sequences of the haemagglutinins (HAs) of one strain of each of the Hav1 and H2 subtypes and of three strains of the H3 subtype of influenza virus have been established. A large external fragment (BHA) of HA can be released from virus particles using the protease bromelain that cleaves the protein close to its carboxyl terminus, which is inserted in the virus membrane (see Fig 1). Here we show that a single disulphide bond joins the two component polypeptide chains BHA1 and BHA2 and establish the location of five intrachain disulphides. These disulphide bonds have been located in the three-dimensional structure of HA which is known to 3 A resolution.
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PMID:Disulphide bonds of haemagglutinin of Asian influenza virus. 746 12

Helper T-cell clones were isolated from BALB/c mice that had been inoculated with purified light chain (HA2) from H3 subtype influenza virus hemagglutinin (HA). The clones were divided into two distinct groups based on their ability to proliferate in response to bromelain-derived HA (BHA) and the light chain derived from it (BHA2), both of which lack the C-terminal 46 amino acid residues of the HA2 chain. The first group contained two I-Ad restricted clones that proliferated in response to BHA and BHA2 and were found to recognize the determinant 96AELLVALEN104. The remaining seven clones were I-Ed restricted, required intact HA2 for proliferation, and responded to synthetic peptides containing the sequence 170RFQIKGVEL178 which spans the bromelain cleavage site. Although all T-cell clones proliferated in response to a wide range of different H3 virus strains, they showed no cross-reactivity with viruses of the H1 or H2 subtype. The T-cell clones from each group were able to provide help to virus-primed B cells allowing them to produce anti-HA antibody in vitro.
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PMID:Conserved determinants for CD4+ T cells within the light chain of the H3 hemagglutinin molecule of influenza virus. 750 81

We have previously shown that alpha-2-O-methyl-5-N-thioacetylneuraminic acid (alpha-Neu5thioAc2Me) has a higher affinity to bromelain-treated hemagglutinin (HA) of influenza A virus than sialic acid from natural sources (Machytka et al., 1993, FEBS Lett. 334, 117-120). We have now compared the inhibitory effects of alpha-Neu5thioAc2Me and other sialic acid analogs on receptor binding and plaque formation of intact influenza A viruses. When alpha-Neu5thioAc2Me was polymerized by conjugation to polyacrylamide, its affinity to HA increased 10(3)-fold. When analyzed by plaque reduction, the alpha-Neu5thioAc2 polymer was about 10 times more efficient as an inhibitor of virus replication than the alpha-Neu5Ac2 polymer, stressing the importance of sulfur at C5. The S-glycoside alpha-2-S-methyl-5-N-thioacetylneuraminic acid (alpha-Neu5thioAc2SMe) had the same affinity to HA as alpha-Neu5thioAc2Me, but was resistant to neuraminidase. The alpha-Neu5thioAc2S polymer interfered with the replication of a wider spectrum of influenza A virus subtypes than the alpha-Neu5thioAc2 polymer. The results indicate that the alpha-Neu5thioAc2S polymer has the potential to be used as an inhibitor of influenza virus infection.
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PMID:Suppression of influenza virus infection by an N-thioacetylneuraminic acid acrylamide copolymer resistant to neuraminidase. 757 3

1,1'-Bis(4-anilino-5-naphthalenesulphonic acid) (bis-ANS) has been shown by fluorescence spectroscopy to bind to bromelain-cleaved influenza haemagglutinin (BHA). The fluorescence intensity of 1.2 microM bis-ANS in the presence of BHA in its low-pH conformation is twenty-fold higher than in the presence of BHA in its neutral-pH conformation. The use of this probe provides a sensitive method for investigating the kinetics of the irreversible conformational change of BHA induced by low pH. At pH5.0 the reaction is described by a rapid burst followed by a double exponential increase in the fluorescence of bis-ANS, with rate constants of 5.2 +/- 0.9 x 10(-3) sec-1 and 6.7 +/- 1.9 x 10(-4) sec-1. This reaction is sensitive to the presence of tert-butylhydroquinone, an inhibitor of the conformational transition of BHA. The dependence of the reaction rate on pH indicates that the acid-induced conformational change is dependent upon the multiple protonation of the neutral-pH conformation of BHA.
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PMID:The kinetics of the acid-induced conformational change of influenza virus haemagglutinin can be followed using 1,1'-bis(4-anilino-5-naphthalenesulphonic acid). 781 41

Activation of the membrane fusion potential of influenza haemagglutinin (HA) at endosomal pH requires changes in its structure. X-ray analysis of TBHA2, a proteolytic fragment of HA in the fusion pH conformation, indicates that at the pH of fusion the 'fusion peptide' is displaced by > 10 nm from its location in the native structure to the tip of an 11 nm triple-stranded coiled coil, and that the formation of this structure involves extensive re-folding or reorganization of HA. Here we examine the structure of TBHA2 with the electron microscope and compare it with the fusion pH structure of HA2 in virosomes, HA2 in aggregates formed at fusion pH by the soluble, bromelain-released ectodomain BHA and HA2 in liposomes with which BHA associates at fusion pH. We have oriented each HA2 preparation for comparison, using site-specific monoclonal antibodies. We conclude that the structural changes in membrane-anchored and soluble HA preparations at the pH of fusion appear to be the same; that in the absence of a target membrane, the 'fusion peptide' of HA in virosomes associates with the virosome membrane so that HA2 is membrane bound at both N- and C-termini, which implies that inversion of the re-folded HA can occur; and that the structural changes observed by X-ray analysis do not result from the proteolytic digestions used in the preparation of TBHA2.
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PMID:Electron microscopy of antibody complexes of influenza virus haemagglutinin in the fusion pH conformation. 783 35

Four immunization protocols were used to obtain cross-reactive influenza type A-specific monoclonal antibodies: (1) repeated administration of purified influenza virus, (2) immunization with bromelain-treated viral particles free of HA and NA, (3) sequential immunization with two strains of different subtypes, and (4) immunization with bromelain-treated particles following tolerization of mice to surface glycoproteins by cyclophosphamide. The fourth approach was shown to be the most effective since a high proportion of hybridomas producing cross-reactive influenza virus type A-specific MAbs were obtained. MAbs of type A specificity were immunochemically characterized and examined for their ability to detect virus in clinical specimens. It was demonstrated that two pairs of the newly prepared MAbs provided excellent reagents for viral detection in clinical specimens using time-resolved fluoroimmunoassay.
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PMID:Preparation of monoclonal antibodies for the diagnosis of influenza A infection using different immunization protocols. 789 42


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