Identification of two novel amyloid A protein subsets coexisting in an individual patient of AA-amyloidosis

Amyloid A protein (AA), the major fibril protein in AA-amyloidosis, is an N-terminal cleavage product of the precursor protein, serum amyloid A (SAA). Using mass spectrometry and amino-acid sequencing, we identified and characterized two novel AA protein subsets co-deposited as amyloid fibrils in an patient having AA-amyloidosis associated with rheumatoid arthritis. One of the AA proteins corresponded to positions 2–76 (or 75) of SAA2α and the other corresponded to positions 2–76 (or 75) of known SAA1 subsets, except for position 52 or 57, where SAA1α has valine and alanine and SAA1β has alanine and valine in position 52 and 57, respectively, whereas the AA protein had alanine at the both positions. Our findings (1), demonstrate that not only one but two SAA subsets could be deposited together as an AA-amyloid in a single individual and (2), support the existence of a novel SAA1 allotype, i.e., SAA1^52,57Ala.     

Primary structure of a protein isolated from reef shark (Carcharhinus springeri) cartilage that is similar to the mammalian C-type lectin homolog, tetranectin.

During the course of characterization of low molecular weight proteins in cartilage, we have isolated a protein from reef shark (Carcharhinus springeri) cartilage that bears a striking resemblance to the tetranectin monomer originally described by Clemmensen et al. (1986, Eur. J. Biochem. 156, 327-333). The protein was isolated by extraction of neural arch cartilage with 4 M guanidine hydrochloride, dialysis of the extract to bring the guanidine to 0.4 M (reassociating proteoglycan aggregates), followed by cesium chloride density gradient removal of the proteoglycans. The amino acid sequence had 166 amino acids and a calculated molecular weight of 18,430. The shark protein was 45% identical to human tetranectin, indicating that it was in the family of mammalian C-type lectins and that it was likely to be a shark analog of human tetranectin. The function of tetranectin is unknown; it was originally isolated by virtue of its affinity for the kringle-4 domain of plasminogen. Sequence comparison of human tetranectin and the shark-derived protein gives clues to potentially important regions of the molecule.     

Environment-specific amino acid substitution tables: tertiary templates and prediction of protein folds.

The local environment of an amino acid in a folded protein determines the acceptability of mutations at that position. In order to characterize and quantify these structural constraints, we have made a comparative analysis of families of homologous proteins. Residues in each structure are classified according to amino acid type, secondary structure, accessibility of the side chain, and existence of hydrogen bonds from the side chains. Analysis of the pattern of observed substitutions as a function of local environment shows that there are distinct patterns, especially for buried polar residues. The substitution data tables are available on diskette with Protein Science. Given the fold of a protein, one is able to predict sequences compatible with the fold (profiles or templates) and potentially to discriminate between a correctly folded and misfolded protein. Conversely, analysis of residue variation across a family of aligned sequences in terms of substitution profiles can allow prediction of secondary structure or tertiary environment.     

美洲蜚蠊机械感受器输出信号的计算机分析

对蜚蠊单个机械感受器诱发反应峰电位的历程及幅度,使用系列分析、栅分析、时序分布、累加密度函数、栅—频分析、特征参数的伪三维隐线显示、峰电位幅度概率密度函数、峰电位间隔概率密度函数等分析方法,获得较多的神经信号间隔编码信息,以揭示刺激和反应之间的复杂关系。峰电位间隔和栅—频分析图由函数经曲线拟合后,分别求得描述其动态过程的时间常数τ_1,τ_2和τ_3,应用上述多种分析显示方法,使研究者更为直观地观察和定量描述刺激—反应间的动态关系。     

利用带有原核增强子样序列的新型载体在大肠杆菌中高效表达人α肿瘤坏死因子

将去除信号肽的人肿瘤坏死因子-α(Tumor necrosis factor-α,TNF-α)cDNA插入到带有原核增强子样序列Px的新型表达载体pBV320中,使TNF cDNA 5′端直接置于大肠杆菌trp启动子下游,采用37℃恒温培养,使TNF在大肠杆菌中获得了高效表达,表达活性达1.35(±0.17)×10~6U/L菌液。表达的TNF-α对L929细胞的毒性作用可被抗人肿瘤坏死因子-α的单克隆抗体所中和。表达菌裂解液作SDS-聚丙烯酰胺凝胶电泳,显示有一条分子量与TNF分子量吻合、约为17000道尔顿的蛋白带。利用DEAE-Sepharose阴离子交换层析及Sephacryl S-200凝胶过滤对上述重组人TNF-α进行纯化,获得电泳纯产品,比活性为1.48×10~6U/mg。     

The acetycholinesterase gene ofAnopheles stephensi

1. The acetylcholinesterase (AChE) gene from the important malaria vector Anopheles stephensi has been isolated by homology to the Drosophila acetylcholinesterase gene. 2. The complete sequence and intron-exon organization has been determined. The encoded protein has 69% identity to Drosophila AChE and 38 and 36% identity to Torpedo AChE and human butyrylcholinesterase, respectively.     

Isolation and partial sequence of goat spleen prothymosin α

Goat prothymosin , a highly acidic polypeptide of pl 3.5, 109 amino acid residues, has been isolated from lymphoid and non-lymphoid tissues of young female goats. Unlike rat, murine and porcine prothymosins , goat prothymosin appears at a higher concentration in the spleen compared with the thymus. The sequence of segments of the polypeptide involving known mutations has been determined, by automatic sequencing of its tryptic peptide fragments. The acidic amino acid-rich segment in the middle of the molecule, including residues 49–83, has not been sequenced. Goat prothymosin closely resembles bovine prothymosin , with only one substitution, proline for alanine at position 85. It also resembles human prothymosin , with only three substitutions. It differs more significantly from rat and murine prothymosins , by two deletions and three substitutions. The results show the highly conserved nature of the molecule, with substitutions at given positions only.Abbreviations ProT Prothymosin - T₁ Thymosin ₁ - MLR Mixed Lymphocyte Response - HPLC High Performance Liquid Chromatography - RIA Radioimmunoassay - B Aspartic acid or Asparagine - Z Glutamic acid or Glutamine     

Codon usage and G+C content in Bradyrhizobium japonicum genes are not uniform

To date, the sequences of 45 Bradyrhizobium japonicum genes are known. This provides sufficient information to determine their codon usage and G+C content. Surprisingly, B. japonicum nodulation and NifA-regulated genes were found to have a less biased codon usage and a lower G+C content than genes not belonging to these two groups. Thus, the coding regions of nodulation genes and NifA-regulated genes could hardly be identified in codon preference plots whereas this was not difficult with other genes. The codon frequency table of the highly biased genes was used in a codon preference plot to analyze the RSRj9 sequence which is an insertion sequence (IS)-like element. The plot helped identify a new open reading frame (ORF355) that escaped previous detection because of two sequencing errors. These were now corrected. The deduced gene product of ORF355 in RSRj9 showed extensive similarity to a putative protein encoded by an ORF in the T-DNA of Agrobacterium rhizogenes. The DNA sequences bordering both ORFs showed inverted repeats and potential target site duplications which supported the assumption that they were IS-like elements.