The gene for the penicillinase from B. licheniformis has been cloned in a functional state on a 1.5 kb DNA fragment and its nucleotide sequence has been determined. A sequence of 307 amino acid residues is infered for the penicillinase precursor. Of these 34 amino acids precede the sequence of the secreted form of the enzyme. This peptide extension shows the features of a signal for secretion and also provides the hydrophobic anchor for the membrane-bound form of the enzyme.

Single-stranded DNA vectors were constructed in vitro by insertion of various DNA fragments into the Intergenic Region of the single-stranded DNA phage fd. These inserts introduce into the phage genome unique cleavage sites for restriction nucleases which are suited for sticky joining in cloning experiments. Since these sites are usually located within genes coding for antibiotic resistance, inactivation of a resistance gene by insertion can be used as a marker for the successful cloning of a DNA fragment. Resistance genes also allow to select for recombinant DNA phages and to minimize the loss of DNA inserts which otherwise becomes significant above an insert size of about one kb. Cloning of several DNA fragments is described and strand separation of double-stranded DNA fragments by means of cloning into fd DNA is given as an example for application of single-stranded DNA vectors.

DNA sequence analysis of the structural gene for Bacillus licheniformis penicillinase has revealed a tetrapeptide sequence of Leu-Ala-Gly-Cys within the NH2-terminal part of the precursor form of penicillinase (pencillin amido-i3-lactamhydrolase, EC 3.5.2.6). The same tetrapeptide occurs in the signal sequence of the prolipoprotein of Escherichia coli, and the cysteine residue in the tetrapeptide of prolipoprotein is modified to form glyceride-cysteine which becomes the NH2 terminus of Braun's lipoprotein. On Penicillinase (penicillin amido-g-lactamhydrolase, EC 3.5.2.6) from Bacillus licheniformis exists in two forms, the exoenzyme which is secreted into the culture medium and the membranebound form which is associated with the membrane (1, 2) presumably via the hydrophobic segment at the NH2 terminus (3). The membrane-bound penicillinase is not a phospholipoprotein because it contains less than 0.02 mol of phosphate per mol of enzyme (3). The structural gene for the penicillinase from B. licheniformis has been cloned on a A-transducing phage (4). The availability of this clone allows study of the expression of this gene both in vitro and in Escherichia coli. In vitro transcription and translation of the penicillinase gene reveals the synthesis of a penicillinase precursor that is larger than the membranebound form (5). The sequence of the NH2-terminal portion of the penicillinase, as deduced from the DNA sequence of the cloned gene, is shown in Fig. 1B (6). The sequence of prepenicillinase includes the tetrapeptide Leu-Ala-Gly-Cys. This is the same tetrapeptide surrounding the site ofposttranslational modification and processing ofprolipoprotein in E. coli (Fig. LA) (1 ,uCi/ ml, 23.5 Ci/mmol), [2-3H]glycerol (50 ,uCi/ml, 6.35 Ci/ 3506The publication costs ofthis article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact.

Derivatives of bacteriophages fd which transduce kanamycin resistance were selected after growth of the phage in an E. coli strain that carried transpoon 5 (Tn5). Different clones of transducing phage and their DNAs were characterized by gel electrophoresis, electron microscopy, and by their ability to multiply in the absence of helper phage. Integration of the intact transposon into the full size phage genome was correlated with an increase in size of the phage particle from 0.95 mu to 1.7 mu, and with the appearance in the phage DNA of the stem loop structure characteristic for single-stranded Tn5 DNA. In non-defective phages the site of insertion was mapped by heteroduplex analysis within the intergenic region of the phage genome. Defective transducing phages were characterized as an insertion of Tn5 into a phage gene, and/or as a partial deletion or duplication of phage and transposon DNA. The size of the transducing phage from different defective clones varied from 0.6 mu to 3.0 mu and was directly proportional to the DNA content. These results demonstrate that filamentous bacteriophage are highly capable to replicate and package very different amounts of foreign DNA.

Abstract. In the article it was shown that one of the factors that significantly affect the mechanism of rolling friction is the mechanism of micro slippage between the balls and the raceway bearing. In this connection was defined the character of friction torque distribution along the contact area of contacting elements.