Short sequence-paper Discovery of the tail tube gene of bacteriophage Mu and sequence analysis of the sheath and tube genes Shigeki Takeda a , Takayo Sasaki 1; b , Akishige Ritani a , Martha M. Howe c , Fumio Arisaka a; * a Department of Life Science, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226, Japan b Department of Biochemistry, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo 060, Japan c Department of Microbiology and Immunology, University of Tennessee-Memphis, Memphis, TN 38163, USA Received 15 April 1998; revised 3 June 1998; accepted 11 June 1998 Abstract The nucleotide sequence was determined for 2.75 kbp of phage Mu DNA encoding the contractile tail sheath protein L. N- terminal sequence analysis of Mu tail tube and sheath proteins identified the open reading frame just downstream of gene L as the tube gene. This clustering and order of the sheath and tube genes appear to be common among the myoviridae. Database homology searches revealed high similarity between the Mu sheath and tube proteins and two proteins in a Haemophilus influenzae Mu-like prophage, suggesting that they are the sheath and tube proteins of that prophage. ß 1998 Elsevier Science B.V. All rights reserved. Keywords : Phage Mu; Tail sheath; Tail tube; DNA sequence; Myoviridae; (Haemophilus in£uenzae) Bacteriophage Mu particles have a complex struc- ture with an eicosahedral head 54 nm in diameter and a contractile tail which consists of a long co- cylindrical structure with a baseplate [1]. The con- tractile outer cylinder is called the `sheath', and the inner cylinder is called the `tube'. The process of contraction involves a dramatic change in Mu sheath morphology as observed by electron microscopy; the length of the sheath decreases from 100 to 56 nm [1^ 3]. At the distal end of the tail, there is a baseplate with six, 31 nm long tail ¢bers that function in spe- ci¢c attachment of the phage to the host cell [1,4]. At the proximal end of the tail is a knob-like neck struc- ture that may serve to join the head to the tail [1,5]. Genes L, M, Y, N, P, Q, V, W, and R have been identi¢ed as involved in the synthesis of Mu tail pro- teins. Mutants defective in these genes produce no detectable tail-like structures but accumulate appar- ently normal full heads, which are functional for phage assembly [5,6]. Such a complex contractile tail apparatus, which is responsible for delivering the phage chromosome into the host cell, is a distinc- tive feature of myoviridae. In our e¡orts to elucidate the structural basis for tail contraction, we have pre- viously determined the primary structure of the sheath and tube proteins of phage T4 [7,8] and Pseu- domonas aeruginosa phage PS17 [9]; here we present the nucleotide sequence of the sheath and tube genes of phage Mu. 0167-4781 / 98 / $19.00 ß 1998 Elsevier Science B.V. All rights reserved. PII:S0167-4781(98)00102-X * Corresponding author. Fax: +81 (45) 924-5805; E-mail : farisaka@bio.titech.ac.jp 1 Present address : Mitsubishi Kasei Institute of Life Sciences, 11 Minami-Ooya, Machida-shi, Tokyo 194, Japan. Biochimica et Biophysica Acta 1399 (1998) 88^92