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M C Graves

Publications and source records attributed to M C Graves.

65 records · Page 4Linked to original sources
PubMed1983

Activity of Euglena gracilis chloroplast ribosomes with procaryotic and eucaryotic initiation factors.

A method that permits the preparation of Euglena gracilis chloroplast 30 S ribosomal subunits that are largely free of endogenous initiation factors and that are active in the binding of fMet-tRNA in response to poly(A, U, G), has been developed. These 30 S subunits have been tested for activity in initiation complex formation with initiation factors from both procaryotes and eucaryotes. We have observed that Escherichia coli IF-2 binds fMet-tRNA nearly as well to Euglena chloroplast ribosomal subunits as it does to its homologous subunits. Neither wheat germ eIF-2 nor Euglena eIF-2A can bind fMet-tRNA efficiently to Euglena chloroplast or E. coli 30 S subunits although both are active with wheat germ 40 S ribosomal subunits. Euglena chloroplast 68 S ribosomes will also bind the initiator tRNA. Both E. coli IF-2 and E. coli IF-3 stimulate this reaction on chloroplast ribosomes with approximately the same efficiency as they do on their homologous ribosomes. E. coli IF-1 enhances the binding of fMet-tRNA to the chloroplast 68 S ribosomes when either IF-2 or IF-3 is limiting. The chloroplast ribosomes unlike E. coli ribosomes show considerable activity over a broad range of Mg2+ ion concentrations.

Binding Sites↗
PubMed1983

Effect of N,alpha-tosyl-L-phenylalanine chloromethyl ketone on measles virus P and M polypeptides.

Treatment of measles virus-infected cells with 1 mM N,alpha-tosyl-L-phenylalanine chloromethyl ketone (TPCK) was observed to change the polyacrylamide gel migration of viral polypeptides P and M. Untreated cells contained P as a mixture of P1 (70,000 daltons) and P2 (65,000 daltons) and M as a 38,000-dalton band M1 and a slightly smaller band, M2. TPCK treatment resulted in conversion of P largely to the 65,000-dalton band and of M to M1 and a slightly slower-migrating band. This effect could also be demonstrated by treating homogenates of infected cells with TPCK, and the evidence suggests that the compound reacts directly with the viral P and M polypeptides and thereby changes their gel migration. TPCK also inhibited measles virus-associated protein kinase, and treatment of virion preparations with the compound resulted in a loss of infectivity; however, it was not possible to directly correlate the inhibitory effect on these two biological functions with the change seen in polypeptides P and M.

Amino Acid Chloromethyl Ketones↗
PubMed1982

Euglena gracilis chloroplast small subunit rRNA. Sequence and base pairing potential of the 3' terminus, cleavage by colicin E3.

RNA sequencing methods have been used to determine sequences at the 3' ends of the small subunit RNAs from Euglena gracilis cytoplasmic and chloroplast ribosomes. The cytoplasmic rRNA sequence, AUCAU psi GOH, has features typical of eukaryotic 18 S rRNAs. The sequence at the 3' terminus of the chloroplast 17 S rRNA, AACAACUCCCOH, differs in several positions from nucleotides conserved in both prokaryotic and eukaryotic small subunit rRNAs, but it does terminate with a pyrimidine tract. Like prokaryotic ribosomes, the chloroplast ribosome displays highly specific binding to purine-rich oligonucleotides. The 30 S subunits select from a random mixture of oligonucleotides only those that contain the sequence GGGAG, which is complementary to the 3' end of 17 S rRNA. The 68S chloroplast ribosome has been shown to be a substrate in vitro for colicin E3. Colicin E3 introduces a cleavage at a position in the chloroplast 17 S rRNA that corresponds exactly to that hydrolyzed in Escherichia coli S rRNA. These results suggest that the 3'-terminal region of 17 S rRNA has an arrangement in the 68 S chloroplast ribosome that may be equivalent to that of the prokaryotic ribosome, with the 3' end exposed in the 30 S subunit for interactions with complementary RNA sequences.

Base Composition↗
PubMed1981

Measles virus polypeptides in infected cells studied by immune precipitation and one-dimensional peptide mapping.

Measles virus does not turn off host cell polypeptide synthesis, making it difficult to precisely identify the polypeptides specified by the virus during the infectious cycle. By using the technique of immune precipitation with measles-specific antisera, the host cell background has been eliminated, and new observations have been made concerning measles virus polypeptides H, P, NP, F, and M. The H polypeptide is first synthesized as a monomer which is processed by further glycosylation and by the formation of disulfide-bonded dimers. Polypeptide P (70,000 daltons) has been found to occur also as a 65,000-dalton molecule, P2, and both forms of the molecule are equally phosphorylated. Polypeptide NP is processed from a cleavage-sensitive form (which undergoes cleavage during the process of isolation to form polypeptide 6 [41,000 daltons]) to a form which is resistant to this cleavage. The fusion and hemolysin polypeptide is first found in the cells as a 55,000-dalton precursor, F0, which is clearly resolved from the NP polypeptide on gel electrophoresis. The measles virus F0 protein identified in previous reports had not been resolved from the 60,000-dalton NP polypeptide. The M protein occurs in the infected cells as two distinct bands, and, as in the case of Sendai virus, one of these two M protein bands represents a phosphorylated form of the other.

Antibodies, Viral↗
PubMed1981

Immunologic and virologic studies of measles inclusion body encephalitis in an immunosuppressed host: the relationship to subacute sclerosing panencephalitis.

An immunosuppressed child with acute lymphoblastic leukemia in clinical remission developed measles inclusion body encephalitis (MIBE). Although measles antigen and nonbudding measles virus nucleocapsids were detected in brain tissue, no virus was isolated. Immune precipitation of measles virus proteins with the patient's serum showed no detectable antibody to virus M protein, a finding that has been reported in subacute sclerosing panencephalitis (SSPE). The virologic and immune precipitation studies suggest a similar virus mutation in MIBE and SSPE. The pathogenesis of the two diseases may also be similar.

Adult↗