Critical arginine residue for maintaining the bacteriophage tail structure.

The addition of 0.2 m l-arginine to various T-even bacteriophage preparations inactivated the virus preparations irreversibly. The virus particles were even more sensitive to added d-arginine and l-homoarginine than to l-arginine but were unaffected by arginine analogues with either an altered carboxyl group or guanidyl group. Treatment of phage T2H with 2,3-butanedione, a reagent which specifically reacts with the guanidyl portion of arginine residues, resulted in the apparent in-activation of most of the virus particles. However, after incubation of the treated particles at pH 7.5 at 37 C for 1 hr in the absence of butanedione, the original virus titer almost completely returned. The reactivation was completely inhibited by the presence of 0.2 m d-arginine. It appeared that the virus protein coat was sufficiently plastic so that the initial conformational change resulting from the alteration of an arginine residue (to possibly an ornithine residue) was at least partially reversible and that the virus tail proteins then refolded to produce a stable and active virus particle. These reactivated virus particles were not sensitive to inactivation by d-arginine but could now be rapidly inactivated by l-ornithine. Virus particles inactivated by arginine have altered tail structures. They have contracted tail sheaths still attached to tail plates and still contain tail cores. These properties of virus particles indicate that there is a free carboxyl group and a guanidyl group spatially equivalent to an arginine residue on one component of the virus tail which bind reversibly by means of polar linkages to another tail component. These bonds maintain the integrity of the virus tail. Added arginine appears to compete with this endogenous viral arginine for the binding sites and then to favor an irreversible conformational change.