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G G Abdurashidova

Publications and source records attributed to G G Abdurashidova.

16 recordsLinked to original sources
PubMed1991

Direct tRNA-protein interactions in ribosomal complexes.

Nucleotide residues in E. coli tRNA(Phe) interacting directly with proteins in pre- and posttranslocated ribosomal complexes have been identified by UV-induced cross-linking. In the tRNA(Phe) molecule located in the Ab-site (pretranslocated complex) residues A9, G18, A26 and U59 are cross-linked with proteins S10, L27, S7 and L2, respectively. In tRNA(Phe) located in the Pt-site (posttranslocated complex) residues C17, G44, C56 and U60 are cross-linked with proteins L2, L5, L27 and S9, respectively. The same cross-links (except for G44-L5) have been found for tRNA in the Pb-site of the pretranslocated ribosomal complex. None of the tRNA(Phe) residues cross-linked with proteins in the complexes examined by us are involved in the stabilization of the secondary structure, but residues A9, G18, A26, G44 and C56 participate in stabilization of tRNA tertiary structure. Since translocation of tRNA(Phe) from Ab- to P-site is accompanied by changes of tRNA contacts with proteins L2 and L27, we postulate that this translocation is coupled with tRNA turn around the axis joining the anticodon loop with the CCA-end of the molecule. This is in agreement with the idea about the presence of a kink in mRNA between codons located in the ribosomal A- and P-sites. In all E. coli tRNAs with known primary structure positions 18 and 56, interacting with L27 protein, when tRNA is located either in A- or P-site, are invariant, whereas positions 17 and 60, interacting with proteins only when tRNA is in the P-site, are strongly conserved. In positions 9, 26 and 59 purines are the preferred residues. In most E. coli tRNAs deviations from the consensus in these three positions is strongly correlated.

Bacterial Proteins↗
PubMed1990

Determination of tRNA nucleotide residues directly interacting with proteins in the post- and pretranslocated ribosomal complexes.

Nucleotide residues of E. coli tRNA interacting directly with proteins in pre- and posttranslocated ribosomal complexes have been identified by analysis of photo-induced tRNA-protein cross-links. A9, G18, A26 and U59 residues of NAcPhePhe-tRNA, located in the Ab-site (pretranslocated complex) have been cross-linked with proteins S10, L27, S7 and L2 respectively. In deacylated tRNA, located in the Pb-site, residues C17, G44, C56 and U60 have been cross-linked with proteins L2, L5, L27 and S9 respectively. The G44-L5 cross-link disappeared after translocation (NAc-PhePhe-tRNA located in the Pt-site).

Base Sequence↗
PubMed1989

Nucleotide residues of tRNA, directly interacting with proteins within the complex of the 30 S subunit of E. coli ribosome with poly(U) and NAcPhe-tRNA(Phe).

With the aid of photoinduced tRNA-protein cross-linking, nucleotide residues A21, U45 and U60 were shown to interact directly with proteins S5, S7 and S9 respectively, in the complex of the 30 S subunit of E. coli ribosome with poly(U) and NAcPhe-tRNA(Phe). These nucleotide residues are located in the central part of the L-form in the tertiary structure of RNA.

Bacterial Proteins↗
PubMed1986

Induction of polynucleotide-protein cross-linkages by ultraviolet irradiation. Peculiarities of the high-intensity laser pulse irradiation.

The efficiency and specificity of RNA-protein cross-linking in the 30S subunit of Escherichia coli ribosomes, induced by low-intensity (10(15) photons cm-2 s-1, 254 nm) and high-intensity [(1.6-6.8) X 10(24) photons cm-2 s-1, 266 nm, pulse duration 10(-8) s] ultraviolet radiation, are studied. Under the former conditions proteins S4, S7 and S9/S11, and under the latter conditions these proteins together with S3, S18 and S20, are cross-linked to 16S RNA. Biphotonic processes operate in the latter case. In the presence of 2-mercaptoethanol cross-linking occurs either directly, via a higher excited state or via activated intermediates with life-times less than 25 ns. Cross-links thus formed are specific, i.e. they are formed between regions of macromolecules which are in contact in the native (non-disturbed) complex prior to excitation. The efficiency of cross-linking (per photon absorbed) is 20-100 times higher upon two-step excitation as compared with single-step excitation and an analysable number of cross-links are produced in a single pulse. Only base U-1239 of 16S RNA is cross-linked to protein S7 by low-intensity radiation, whereas the adjacent base, G-1240 is also involved in laser-induced cross-linking. A transition from the former to the latter conditions allows one to reduce the duration of irradiation from several minutes to several nanoseconds.

Bacterial Proteins↗
PubMed1986

Structural characteristics and classification of some tRNA-binding sites of elongating Escherichia coli ribosome.

Ultraviolet(254 nm)-irradiation-induced cross-linkages in ribosomal complexes allowed identification of proteins in contact with tRNA at different elongation steps. Both the set and the ratio of cross-linked proteins, i.e. the structural characteristics of the tRNA-binding sites of the ribosome, were shown to depend strongly not only on the position of the mRNA codon with which tRNA interacts as a component of a ribosomal complex, but also on its functional state, i.e. on the elongation step. A new classification of tRNA-binding sites of ribosome is suggested.

Bacterial Proteins↗
PubMed1985

Intersubunit RNA-protein contacts in pre- and post-translocated E. coli ribosome.

Ribosomal proteins participating in intersubunit RNA-protein contacts (directly interacting with RNA of the opposite subunit) were determined by means of ultraviolet-induced cross-links in pre- and post-translocated ribosomal complexes, as well as in the free 70 S ribosome (tight couple) of E. coli. In these 3 complexes at least L1 and L9 proteins interact with 16 S RNA, while S6, S9/11 and S15 react with 23 S RNA. All these proteins ('hinge-joint' proteins) are clustered on the small protuberance of the 50 S subunit and on the platform of the 30 S subunit. Reduction in the number of other (variable) intersubunit RNA-protein contacts in the course of transition from the tight couple to the pre- and, finally, to the post-translocated state, demonstrates gradual loosening of intersubunit interactions in 70 S ribosome. Such a loosening ('opening') of the 70 S ribosome is determined by conformational changes in ribosomal subunits and/or in their relative arrangement, conjugated with alteration of the functional state of the ribosomal complex.

Bacterial Proteins↗
PubMed1985

[Changes in subunit conformation and their reciprocal configuration in the transition from the pretranslocated to the posttranslocated state].

RNA-protein contacts in pretranslocated and posttranslocated states of E. coli ribosomes have been determined by means of UV-induced cross-linking. In the two functional states as well as in free 70C ribosome, the same proteins are involved in RNA-protein intersubunit contacts, located in the region of L1 protuberance (left side of 70S ribosome). The transition from pre- to posttranslocated state is accompanied by disappearance of RNA-protein contacts in the region of L7/L12 stalk. This favours the locking-unlocking model of the translating ribosome.

Escherichia coli↗
PubMed1985

[General method of isolation and analysis of polynucleotide fragments cross-linked with proteins].

A fragment of 16S RNA, cross-linked to S7 protein by UV irradiation of the 30S subunit of E. coli ribosome, was obtained by the action of T1 ribonuclease on the irradiated nucleoprotein. The digest was treated with polynucleotide kinase in the presence of [gamma-32P]ATP and the S7-cross-linked oligonucleotides were isolated. An individual oligonucleotide attached to S7 protein was obtained after proteinase treatment of the respective spot followed by electrophoresis. Sequencing of this oligonucleotide established its structure as 1233-1240 fragment of 16S RNA, the U1239 residue being the site of the S7 cross-linking. The developed general approach can be used for localizing protein - cross-linked residues in polynucleotides, whatever is the procedure employed for cross-linking.

Base Sequence↗
PubMed1983

Preparation and properties of monomercurated tRNA.

Monomercurated tRNA has been prepared by exhaustive treatment of mercaptoethanol on polymercurated tRNA under non-denaturing conditions. The remained mercury atom is stable toward ultraviolet (254 nm) irradiation up to absorption of 100 quanta/nucleotide, but could be easily removed by mercaptoethanol under denaturing conditions. Monomercurated tRNA quantitatively binds to thiopropyl-Sepharose and can be completely desorbed by mercaptoethanol-containing solutions. Monomercurated tRNA is similar to the starting tRNA preparation in efficiency and specificity of aminoacylation and in factor-dependent polypeptide synthesis in vitro.

Chemical Phenomena↗
PubMed1979

Polynucleotide-protein interactions in the translation system. Identification of proteins interacting with tRNA in the A- and P-sites of E. coli ribosomes.

Ultraviolet irradiation (lambda = 254 nm) of ternary complexes of E. coli 70 S ribosomes with poly(U) and either Phe-tRNAPhe (in the A-site) or NAcPhe-tRNAPhe (in the P-site) effectively induces covalent linking of tRNA with a limited number of ribosomal proteins. The data obtained indicate that in both sites tRNA is in contact with proteins of both 30 S and 50 S subunits (S5, S7, S9, S10, L2, L6 and L16 proteins in the A-site and S7, S9, S11, L2, L4, L7/L12 and L27 proteins in the P-site). Similar sets of proteins are in contact with total aminoacyl-tRNA and N-acetylaminoacyl-tRNA. However, here no contacts of tRNA in the P-site with the S7 and L25/S17 proteins were revealed, whereas in the A-site total aminoacyl-tRNA contacts L7/L12. Proteins S9, L2 and, probably, S7 and L7/L12 are common to both sites.

Binding Sites↗
PubMedDate not supplied

[Proteins contacting with peptidyl-tRNA at the A-site of the Escherichia coli ribosome after enzymatic and non-enzymatic binding of aminoacyl-tRNA].

Proteins contacting (directly interacting) with peptidyl-tRNA in the A-site of E. coli ribosome were determined by means of ultraviolet-induced RNA-protein cross-linking. It has been shown that upon enzymatic binding of Phe-tRNAPhe with the posttranslocated ribosome and following transpeptidation, the peptidyl-tRNAPhe directly interacts with proteins S5, S10, L6, L16 and S13/S14/L27, while upon non-enzymatic binding--with S5, S10, L2, L6 and L16. These data evidenced, that the difference in tRNA-protein interactions upon enzymatic and non-enzymatic binding of Phe-tRNAPhe to the ribosome does not prevent the following step and remains after transpeptidation.

Escherichia coli↗
PubMedDate not supplied

[Contacts of ribosomal proteins with tRNAPhe and 16S RNA in analogs of the 30S initiation complex].

Direct RNA-protein contacts have been studied by means of ultraviolet-induced (254 nm) cross-links inside complexes of NAcPhe-tRNAPhe, Phe-tRNAPhe and deacylated tRNAPhe with poly(U)-charged 30S subunit of Escherichia coli ribosome. In the first two complexes tRNA directly contacts with the similar sets of proteins (S4, S5, S7, S9/S11; S6 and S8 are found only in the second complex). These sets are similar to that in the fMet-tRNAfMet X 30S X mRNA complex, evidencing similar disposition of tRNAs in these three complexes. 16S RNA contacts in free 30S subunit mainly with proteins S4, S7 and S9/S11. In both complexes, containing NAcPhe-tRNAPhe and Phe-tRNAPhe, 16S RNA contacts with essentially the same proteins (S4, S5, S7, S8, S9/S11, S10, S15, S16 and S17) and in the same ratio, evidencing similar conformation of 30S subunit in these two complexes. In the third complex deacylated tRNAPhe contacts with proteins S4, S5, S6, S8, S9/S11 and S15, 16S RNA-protein interaction differs from those in the first two complexes by a remarkable decrease of cross-linked proteins S8, and S9/S11 and by the appearance of a large amount of cross-linked proteins(s) S13/S14. Hence, this complex differs from the first two by conformation of 30S subunit and, probably, by disposition and/or conformation of tRNA.

Bacterial Proteins↗
PubMedDate not supplied

[Ribosomal proteins interacting with Phe-tRNAPhe during enzymatic binding with translating ribosome before and after the release of the elongation factor EF-Tu].

Proteins, directly interacting with tRNA in R- and A-sites of E. coli ribosome were determined by means of ultraviolet-induced RNA-protein cross-links. It is shown, that tRNAPhe in the R-site (upon enzymatic binding of the ternary complex Phe-tRNAPhe. X Tu X GMPPCP to ribosome) directly interact with factor Tu and ribosomal proteins S4, S5, S8 and L6, while in the A-site (upon binding of Phe-tRNAPhe X Tu X GTP, GTP hydrolysis, Tu release and transpeptidation)--with proteins S5, S10, L6, L16 and S13/S14/L27.

Escherichia coli↗