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J. Bacteriol., 11 1996, 6258-6265, Vol 178, No. 21
S Hashemolhosseini, YD Stierhof, I Hindennach and U Henning
Assembly of tail fibers of coliphage T4 requires the action of helper
proteins. In the absence of one of these, protein 38 (p38), p37,
constituting the distal part of the long tail fiber, fails to oligomerize.
In the absence of the other, p57, p34 (another component of the long tail
fiber), p37, and p12 (the subunit of the short tail fiber) remain
unassembled. p38 can be replaced by the Tfa (tail fiber assembly) protein
(pTfa) of phage lambda, which has the advantage of remaining soluble even
when produced in massive amounts. The mechanisms of action of the helpers
are unknown. As a first step towards elucidation of these mechanisms, p57
and pTfa have been purified to homogeneity and have been crystallized. The
identity of gene 57 (g57), not known with certainty previously, has been
established. The 79- residue protein p57 represents a very exotic
polypeptide. It is oligomeric and acidic (an excess of nine negative
charges). It does not contain Phe, Trp, Tyr, His, Pro, and Cys. Only 25
N-terminal residues were still able to complement a g57 amber mutant,
although with a reduced efficiency. In cells overproducing the protein, it
assumed a quasi-crystalline structure in the form of highly ordered fibers.
They traversed the cells longitudinally (and thus blocked cell division)
with a diameter approaching that of the cell and with a hexagonal
appearance. The 194-residue pTfa is also acidic (an excess of 13 negative
charges) and is likely to be dimeric.
Copyright © 1996, American Society for Microbiology
Characterization of the helper proteins for the assembly of tail fibers of coliphages T4 and lambda
Max-Planck-Institut fur Biologie, Tubingen, Germany.
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