Gene Arrangement within the Unique Long Genome Region of Infectious Laryngotracheitis Virus Is Distinct from That of Other Alphaherpesviruses

The genome of the avian alphaherpesvirus infectious laryngotracheitis virus (ILTV) comprises ca. 155 kbp of which ca. one-third have been sequenced so far. To gain additional sequence information we analyzed two stretches of 15.5 and 1.9 kbp of the ILTV unique long (U_L) genome region. The larger fragment contains homologs of the herpes simplex virus (HSV) UL23 (thymidine kinase) and UL22 (glycoprotein H) genes followed by five open reading frames (ORF) encoding putative proteins of 334 to 410 amino acids which exhibit no homology to any known herpesvirus protein. RNA analyses showed that these unique ILTV genes are indeed expressed. An origin of replication separates this cluster of unique genes from a conserved gene cluster consisting of the UL45, UL46, UL48, UL49, UL49.5, and UL50 homologs. The absence of UL47 from this position coincides with the localization of a UL47-homologous ORF within the unique short (U_S) region of the ILTV genome (M. Wild, S. Cook, and M. Cochran, Virus Genes 12:107–116, 1996). Within the second analyzed region the ILTV UL21 homolog was found adjacent to the UL44 gene. We thus identified five novel herpesvirus genes in ILTV and present evidence for a large internal inversion in the ILTV U_L region, in contrast to the collinear genomes of other alphaherpesviruses. Interestingly, a similar inversion is also present in the porcine alphaherpesvirus pseudorabies virus.     

粗糙脉孢菌基因组分泌蛋白的初步分析

文章报道利用信号肽预测软件SignalP v3.0和PSORT,跨膜螺旋结构预测软件TMHMMv2.0和THUMBUP,GPI-锚定位点预测软件big-PI Predictor和亚细胞器中蛋白定位分布预测软件TargetP v1.01对粗糙脉孢菌全基因组数据库中已公布的10 082个氨基酸序列进行预测分析。结果表明在粗糙脉孢菌中有437个蛋白为分泌蛋白,编码这些蛋白最小的可读框（open reading frame,ORF）为252 bp,最大为6 604 bp,平均1 433 bp,分泌蛋白信号肽长度介于15~59个氨基酸之间。在437个分泌蛋白中,205个具有功能描述,主要包括各种酶类、细胞能量生成、运转以及自身修复、防卫等多种功能。这些蛋白所参与的生化过程可能发生在膜外的周质空间或是菌体外的场所,为该物种营养的摄取,以及对环境做出响应服务。      

A Comparative Structural Analysis of the Flagellin Monomers of Caulobacter crescentus Indicates that These Proteins Are Encoded by Two Genes

The flagellum of Caulobacter crescentus is composed of two flagellin polypeptide monomers which are distinguished by molecular weight and are closely related by biochemical and immunological criteria (C. Lagenaur and N. Agabian, J. Bacteriol. 132:731-733, 1977). The synthesis and assembly of these two flagellin proteins are developmentally regulated, and the periodicity of expression for each is distinct (C. Lagenaur and N. Agabian, J. Bacteriol. 135:1062-1069, 1978; M. A. Osley, M. Sheffery, and A. Newton, Cell 12:393-400, 1977). To understand the genetic and functional relationship between the 25,000- and 27,500-molecular-weight flagellins of C. crescentus CB15, a detailed comparative analysis of their protein structure was made, using a number of techniques, including one- and two-dimensional peptide mapping, a novel procedure of peptide alignment, and amino terminal amino acid sequence analysis. The tryptic peptides generated by each of the flagellins were compared by two-dimensional thin-layer chromatography. This peptide map analysis indicated that approximately 36% of the peptides generated from these two proteins had similar migration properties. Together with biochemical and immunological criteria, the two-dimensional peptide map suggested some structural relatedness between the monomers. However, a comparison of peptide fragments generated during partial protease digestion of each protein by a method of one-dimensional mapping indicated that the two proteins are structurally unique. A peptide alignment technique was developed to directly compare the primary structure of these proteins. In the peptide alignment procedure the amino terminus of each protein is radioactively labeled. After partial enzymatic digestion, the peptides are fractionated by polyacrylamide gel electrophoresis: those labeled at the amino terminus are then resolved by subsequent autoradiography. Each digest contains a family of amino-terminal-labeled fragments, the sizes of which reflect the sequential alignment of cleavage sites in the protein. A comparison of the alignment of specific cleavage sites of the two flagellins by this technique further established that each flagellin is structurally unique, particularly in the carboxyl terminal region. Finally, comparison of the amino terminal amino acid sequences indicated that the amino terminal region of both flagellins is highly conserved, but that the two polypeptides are clearly not identical. These findings strongly indicate that the two flagellins are encoded by distinct genetic loci and are not the product of novel processing of a single larger precursor.