Accession no.Y00433 cDNAs encoding human glutathione peroxidase were isolated from a liver library prepared as described (1) by hybridization with a synthetic oligonucleotide (shown with the closed bar) to the 5' and 3' ends of the mouse genomic DNA sequence reported elsewhere (2). The sequence of 1134 bp minus the poly A tail of the longest cDNA clone is presented below with the predicted amino acid sequence. An asterix indicates the selenocystein at the position of the in-frame TGA codon. Comparison of our data with those of mouse (2) revealed 84% homology at the nucleotide level and 87% homology at the amino acid level.

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Cosmid pR4Cl is a derivative of multicopy plasmid pIJ365 which has an insertion of the cos (cohesive end site) region of actinophage R4 [T. Morino, H. Takahashi and H. Saito, Mol. Gen. Genet., 198, 228 (1985)]. When the donor R4 phage was propagated in S. lividans carrying the plasmid, the phage lysate contained transducing particles which encapsulated head-to-tail concatemers of the plasmid DNA.These particles could mediate transfer of the plasmid at a high frequency. We examined conditions that gave a maximum transduction frequency of cosmid pR4Cl. Conditions which depress R4 phage propagation, such as incubation of recipient S. parvulus at a high temperature, improved the frequency. Obviously such conditions minimized the lethal effect of viable phage propogation. The highest transduction frequency obtained so far was around 3 x lO~3 transductants per infected phage when S. lividans was used as the recipient. This was about 30 per cent of the cosmid transducing particles estimated from the cosmid DNA content in the transducing lysate. The significance of cosmid transduction for gene manipulation in Streptomyces strains is also discussed.The protoplast-PEG (polyethyleneglycol) method has been developed and used for the transformation and transfection of Streptomyces strains.2~4) Preparation and regeneration of protoplasts are critical steps of the method.5) Optimal conditions for protoplast formation and regeneration vary from strain to strain. In general it takes a long time to develop a protoplast-PEG tranformation system in a new Streptomyces strain. In this connection it* is desirable to develop a novel plasmid transfer system applicable for various Streptomyces strains.Previously we reported the construction of cosmid pR4Cl using the cos(cohesive ends site) of actinophage R4 and a multicopy plasmid pIJ365.1>6) Wedemonstrated that the cosmid DNAwas encapsulated in R4 phage particles as head-to-tail concatemers and transferred to newhosts by infection. This signifies that the plasmid DNAcontaining the cos sequence can be transferred to other strains without using the rather laborious protoplast-PEG procedure. Wecalled this procedure R4 phagemediated cosmid-transduction.In this paper we examined conditions which gave maximum cosmid-transduction. The significance and usefulness of the method are also discussed. MATERIALS AND METHODSa) Media and strains. YS and NB media were described in previous papers.7'8) YSagar plates were used for spore formation of Streptomyces strains. NBmediumwas used for preparation of phage lysates. Streptomyces lividans 66 and S. parvulus 2297 were described in previous papers.8' 9) CosmidpR4Cl was constructed by inserting the cos site of R4 phage into a multicopy plasmid pIJ365X) (Fig. 1). b) Preparation ofphage and plasmid DNA.R4 phage was propagated and titrated according to the method

A chymotrypsin‐like protease was purified to homogeneity from human tonsils by a series of Chromatographie procedures. The purified enzyme gave a single protein band with an apparent molecular mass of 30 kDa on SDS‐PAGE. The sequence of the first 21 amino acids at the N‐terminus of the enzyme was determined. A cDNA for the enzyme was cloned by PCR amplification from extracted tonsillar mRNA using a supposed N‐terminal oligonucleotide primer and a conserved C‐terminal primer of the chymase family. The deduced amino acid sequence of the isolated clone was identical to that of human chymase in connective tissue‐type mast cells from heart except for a Ser instead of a Cys at the N‐terminal 7th position.