THE RIBOSOMAL RNA INTRONS OF CALLIPHORA ERYTHROCEPHALA AND THE CALMODULIN GENE OF DROSOPHILA MELANOGASTER (INSECTS)
[摘要] The available cloned examples of the intron-28S coding sequence junctions from the rDNA of Calliphora erythrocephala have been sequenced. These introns interrupt the rDNA at the same position as the type 1 intron family first detected in D. melanogaster and D. virilis. A duplication of 14 bp of the 28S rRNA coding sequence surrounds a shortened 2.8 kb version of the major genomic length class of introns. This duplication is characteristic of the type 1 rDNA intron family in D. melanogaster and D virilis. Comparison of the intron sequences from the three Dipteran flies has revealed considerable homology between the 3;; intron sequences of C. erythrocephala and D. virilis. The 28S coding sequences are highly conserved between these flies. However, a region of diverence has been located and found to correspond to the eukaryotic analogue of the L1 ribosomal protein binding site of the prokaryotic 23S rRNA. A set of overlapping phage clones representing 20.5 kb of the region surrounding the calmodulin gene of D. melanogaster has been isolated from a genomic library. Mapping of the protein coding regions suggests that the calmodulin gene is divided into four exons and three introns. Intron A has separated the initiation codon from the coding regions. Introns B and C, beween amino acids 58 and 59 and amino acids 139 and 140, respectively, split two of the four calcium binding domains. The amino acid sequence of residues 1 through 139 of calmodulin has been deduced from the DNA sequence. In comparison to the mammalian calmodulin sequences, there is a single amino acid substitution at position 99, where phenylalanine replaces tyrosine. A comparison of the D. melanogaster calmodulin gene sequences to other known calmodulin genes shows from 79% to 85% homology.
[发布日期] [发布机构] Rice University
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