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S Noiman

Publications and source records attributed to S Noiman.

10 recordsLinked to original sources
PubMed2001

Modeling the 3D structure of GPCRs from sequence.

G-protein-coupled receptors (GPCRs) are a large and functionally diverse protein superfamily, which form a seven transmembrane (TM) helices bundle with alternating extra-cellular and intracellular loops. GPCRs are considered to be one of the most important groups of drug targets because they are involved in a broad range of body functions and processes and are related to major diseases. In this paper we present a new technology, named PREDICT, for modeling the 3D structure of any GPCR from its amino acid sequence. This approach takes into account both internal protein properties (i.e., the amino acid sequence) and the properties of the membrane environment. Unlike competing approaches, the new technology does not rely on the single known structure of rhodopsin, and is thus capable of predicting novel GPCR conformations. We demonstrate the capabilities of PREDICT in reproducing the known experimental structure of rhodopsin. In principle, PREDICT-generated models offer new opportunities for structure-based drug discovery towards GPCR targets.

Amino Acid Sequence↗
PubMed1995

Detection of histidine-phospho-proteins in animal tissues.

In this report we outline a protocol for rapid detection of histidine phosphoproteins in cellular crude extracts prepared from different tissues. The nature of the phosphorylated amino acid residues was confirmed by determination of their stability under different pH conditions and by direct phospho-amino acid analysis. Furthermore, DEPC treatment that can selectively modify the histidine residues blocks the phosphorylation. Interestingly, the phosphoprotein pattern detected under these conditions in four different tissues is very similar, suggesting that these proteins play important roles in biochemical pathways shared by many cells and tissues.

Animals↗
PubMed1994

The X protein of hepatitis B virus has a ribo/deoxy ATPase activity.

The X protein (pX) of hepatitis B virus (HBV) is a general transcription regulator and directly associated with the transcription machinery. pX cannot bind DNA directly but interacts with cellular factors that bind the regulatory elements. There is an accumulation of evidence concerning different activities exerted by pX in transfected cells; nevertheless, the function and the biochemical properties of the protein are unknown. Biochemical analysis of bacterially expressed pX revealed that the protein possesses hydrolytic activity specific for adenine nucleotides with a Km of approximately 95 microM. This ATPase (dATPase) activity is not DNA-dependent. Mutation analysis revealed that the 88-119 amino-acid region of pX is required for its maximal activity. The putative involvement of (d)ATPase activity in the mechanism of transcription stimulation exerted by pX may be proposed by a certain analogy to the activity of transcription factors which participate in the initiation complex.

Adenosine Triphosphatases↗
PubMed1993

Mild cystic fibrosis and normal or borderline sweat test in patients with the 3849 + 10 kb C-->T mutation.

Different mutations in the cystic fibrosis (CF) gene appear to contribute to heterogeneity of the CF phenotype. We investigated 15 patients with CF who have the 3849 + 10 kb C-->T mutation. All were Ashkenazi Jews. Their clinical features were compared with those of CF patients with the delta F508/delta F508, W1282X/W1282X, W1282X/delta F508 mutations, which are known to be associated with a severe disease. Patients with the 3849 + 10 kb mutation were older, had been diagnosed as having CF at a more advanced age, and were in a better nutritional state. Sweat chloride values were normal (below 60 mmol/L) in 5 3849 + 10 kb patients (33%). 4 of these patients and 6 others (total 66%) had normal pancreatic function. However, age-adjusted pulmonary function did not differ between the two groups. None of the patients with 3849 + 10 kb C-->T had had meconium ileus or had liver disease or diabetes mellitus. We conclude that this mutation is associated with a mild type of CF.

Age Factors↗
PubMed1993

Structural and functional characterization of rev-like transcripts of equine infectious anemia virus.

Three cDNA clones representing structurally distinct transcripts were isolated from a cDNA library prepared from cells infected with equine infectious anemia virus (EIAV) by using a probe representing the S3 open reading frame, which is thought to encode Rev. One species, designated p2/2, contained four exons and was identical to a previously described polycistronic mRNA that encodes Tat. This transcript was predicted to also direct the synthesis of a truncated form of the transmembrane protein and a putative Rev protein whose N-terminal 29 amino acids, derived from env, are linked to S3 sequences. The second cDNA, p176, also consisted of four exons which were generated by two of three of the same splicing events that occur with p2/2 but not with the Tat mRNA. The alternative splice site giving rise to the second exon of p176 results in a bicistronic message that would encode the same transmembrane and Rev proteins as p2/2. The first exon of the third transcript, p20, was identical to those of p2/2 and p176 but was spliced directly to S3. This monocistronic message could encode a second form of Rev that lacks env sequences, provided that Rev synthesis would initiate at a non-AUG codon. The coding capacity of each cDNA was assessed in a eukaryotic system using S3 antisera. Two putative Rev proteins with apparent molecular masses of 18 and 16 kDa were expressed by p2/2 and p176, while p20 expressed only a 16-kDa species. Analysis of EIAV-infected cells with S3 antisera revealed the presence of an 18-kDa protein. Surprisingly, the same protein was detected in purified virions. By using a reporter construct, the chloramphenicol acetyltransferase gene linked to EIAV env sequences, we were able to demonstrate greatly enhanced chloramphenicol acetyltransferase activity in cells cotransfected with this construct and any of the three cDNAs.

Amino Acid Sequence↗
PubMed1991

The Tat protein of equine infectious anemia virus is encoded by at least three types of transcripts.

Nucleotide sequence analysis of a cDNA library of EIAV-infected canine cells established a complex pattern of gene expression, characterized by alternatively spliced polycistronic transcripts. The EIAV tat gene product was shown to be encoded by at least three species of mRNA which differed in their ability to trans-activate the EIAV LTR upon expression in canine cells. The most active cDNA was monocistronic, consisting of three exons. The most abundant cDNA in the library contained four exons and was identical to a polycistronic transcript previously described (Noiman et al., 1990b) which contains open frames for Tat, putative Rev, and truncated transmembrane proteins. Products consistent in size with those predicted for these last two proteins could be detected in in vitro translation experiments. The third Tat message, another four-exon form, also potentially encodes an amino terminally truncated transmembrane protein. In vitro mutagenesis experiments and analysis of subgenomic and partial cDNA clones confirmed and extended previous findings that S1 sequences are essential for trans-activation and that Tat translation initiates at a non-AUG codon either in the full-length Tat message or in the genomic S1 open reading frame. The Tat protein (8 kDa) was detected in cells transfected with a Tat cDNA construct and in canine cells persistently infected with EIAV. The Tat activity of polycistronic mRNAs was lower than that of the monocistronic form, suggesting that the expression of the EIAV trans-activator may be subject to several levels of posttranscriptional control.

Amino Acid Sequence↗
PubMed1990

Identification of sequences encoding the equine infectious anemia virus tat gene.

Equine infectious anemia virus (EIAV), a lentivirus, encodes a trans-activator (tat) which stimulates gene expression directed by the viral long terminal repeat (LTR). This function has been previously shown by us and others to be encoded by sequences within the middle region of the EIAV genome in which two short open reading frames, S1 and S2, reside. In the present study, by using in vitro mutagenesis, we show that disruption of S1, but not S2, completely abolished trans-activation. Addition of oligonucleotides complementary to S1 to cells transfected with a tat expression vector resulted in inhibition of trans-activation. EIAV cDNAs were isolated from a library of EIAV-infected cells constructed by using a eukaryotic expression vector. One cDNA clone which contained S1 sequences was able to trans-activate the EIAV LTR. Sequence analysis of this cDNA clone revealed that, in addition to S1, two other open reading frames were present. The cDNA still retained its activity when the latter two sequences were deleted.

Amino Acid Sequence↗
PubMed1990

Pattern of transcription of the genome of equine infectious anemia virus.

The pattern of expression of the equine infectious anemia virus (EIAV) genome in a persistently infected canine cell line was determined. Five EIAV-specific transcripts (8.2, 5.0, 4.0, 2, and 1.8 kilobases [kb]) were detected by using subgenomic restriction enzyme fragments of EIAV DNA and EIAV-specific oligonucleotides as probes. The 8.2-kb mRNA could be shown to represent viral genomic RNA, whereas the smaller transcripts were generated by splicing events. Evidence was obtained that indicated that each subgenomic RNA species shared a common 5'-splice donor. The 5.0-kb mRNA was found to be expressed at relatively low levels, was difficult to detect consistently, and appeared to be generated by a single splicing event which linked the 5' exon to the 3' region of pol. The 4.0-kb transcript was concluded to be the env mRNA on the basis of its hybridization pattern with the various probes and its abundance. The 2-kb species was found to be multiply spliced and was encoded by sequences derived from orf2 but was not detected by probes representing 3'-env/3'-orf sequences. The 1.8-kb species was shown to consist of sequences representing orf1, part of orf2, and the 3'-orf/env and may represent the message for the EIAV trans-activator gene.

Amino Acid Sequence↗
PubMed1982

Malathion resistance in Tribolium strains and their hybrids: inheritance patterns and possible enzymatic mechanisms (Coleoptera, Tenebrionidae).

(1) The genetics of malathion resistance in two strains of the flour beetle, Tribolium castaneum, was investigated. In CTC-12, resistance is polygenic, while in Kano, it is due to a dominant allele at a single autosomal locus. Reciprocal hybrids with the susceptible control strains bb and pp showed an overdominant response in particular when Kano was the male parent in the original cross. (2) Three possible genetic mechanisms to explain these results are discussed. The model which best explains the genetic results, particularly the difference between the reciprocal crosses, assumes a modifier resistance allele on the Y chromosome. (3) The levels of activity of total esterases, carboxylesterases, mixed-function oxidases, epoxide hydrase, and glutathione transferase in the parent strains and their hybrids were measured quantitatively. Although total esterase activity may not be relevant for the breakdown of malathion, it was inhibited by the pesticide. The activity of the microsomal enzymes was high in CTC-12, low in bb, and intermediate in the hybrids, while carboxylesterases were very active in Kano as well as in the hybrids with bb and low in the latter. These patterns agree with the genetics of resistance in the two strains. A higher level of GSH transferase in the Kano x bb hybrids than in Kano seems to indicate a possible biochemical mechanism for their overdominant resistance.

Animals↗