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1.
Eur J Biochem ; 271(15): 3136-45, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-15265033

RESUMO

The primary structures of N-terminal 19-mer peptides, released by limited trypsin treatment of coat protein (CP) subunits in intact virions of three potato virus X (PVX) isolates, were analyzed. Two wild-type PVX strains, Russian (Ru) and British (UK3), were used and also the ST mutant of UK3 in which all 12 serine and threonine residues in the CP N-terminal segment were replaced by glycine or alanine. With the help of direct carbohydrate analysis and MS, it was found that the acetylated N-terminal peptides of both wild-type strains are glycosylated by a single monosaccharide residue (galactose or fucose) at NAcSer in the first position of the CP sequence, whereas the acetylated N-terminal segment of the ST mutant CP is unglycosylated. Fourier transform infrared spectra in the 1000-4000 cm(-1) region were measured for films of the intact and in situ trypsin-degraded PVX preparations at low and high humidity. These spectra revealed the presence of a broad-band in the region of valent vibrations of OH bonds (3100-3700 cm(-1)), which can be represented by superposition of three bands corresponding to tightly bound, weakly bound, and free OH groups. On calculating difference ('wet' minus 'dry') spectra, it was found that the intact wild-type PVX virions are characterized by high water-absorbing capacity and the ability to order a large number of water molecules on the virus particle. This effect was much weaker for the ST mutant and completely absent in the trypsin-treated PVX. It is proposed that the surface-located and glycosylated N-terminal CP segments of intact PVX virions induce the formation of a columnar-type shell from bound water molecules around the virions, which probably play a major role in maintaining the virion surface structure.


Assuntos
Proteínas do Capsídeo/química , Proteínas do Capsídeo/metabolismo , Potexvirus/metabolismo , Subunidades Proteicas/química , Subunidades Proteicas/metabolismo , Vírion/metabolismo , Água/química , Sequência de Aminoácidos , Proteínas do Capsídeo/genética , Metabolismo dos Carboidratos , Carboidratos/análise , Carboidratos/química , Cromatografia Líquida de Alta Pressão , Eletroforese em Gel de Poliacrilamida , Glicosilação , Hidrólise , Dados de Sequência Molecular , Mutação/genética , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/metabolismo , Potexvirus/química , Subunidades Proteicas/genética , Alinhamento de Sequência , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Espectroscopia de Infravermelho com Transformada de Fourier , Tripsina/metabolismo , Vírion/química
2.
Eur J Biochem ; 270(16): 3300-8, 2003 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-12899688

RESUMO

Spatial organization of wild-type (strain U1) tobacco mosaic virus (TMV) and of the temperature-sensitive TMV ts21-66 mutant was compared by tritium planigraphy. The ts21-66 mutant contains two substitutions in the coat protein (Ile21-->Thr and Asp66-->Gly) and, in contrast with U1, induces a hypersensitive response (formation of necroses) on the leaves of plants bearing a host resistance gene N' (for example Nicotiana sylvestris); TMV U1 induces systemic infection (mosaic) on the leaves of such plants. Tritium distribution along the coat protein (CP) polypeptide chain was determined after labelling of both isolated CP preparations and intact virions. In the case of the isolated low-order (3-4S) CP aggregates no reliable differences in tritium distribution between U1 and ts21-66 were found. But in labelling of the intact virions a significant difference between the wild-type and mutant CPs was observed: the N-terminal region of ts21-66 CP incorporated half the amount of tritium than the corresponding region of U1 CP. This means that in U1 virions the CP N-terminal segment is more exposed on the virion surface than in ts21-66 virions. The possibility of direct participation of the N-terminal tail of U1 CP subunits in the process of the N' hypersensitive response suppression is discussed.


Assuntos
Mutação , Vírus do Mosaico do Tabaco/química , Trítio , Proteínas do Capsídeo/química , Interações Hospedeiro-Parasita/genética , Interações Hospedeiro-Parasita/fisiologia , Contagem de Cintilação , Vírus do Mosaico do Tabaco/genética
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