COMMON LOCALIZATION OF RETENTION DETERMINANTS IN HEPATITIS-B VIRUS L-PROTEIN FROM DIFFERENT STRAINS

Hepatitis B virus L protein is retained intracellularly, and trans-inh ibits secretion of the related S and M proteins, as particulate HBsAg, at high L/S-M ratios, Comparison of equivalent A and D strain mutants suggested that the retention mechanism does not vary with genotype, C ontrary to an earlier suggestion, the N-terminal extension specific fo r A-C strains was found to be inactive as a retention signal. Intact L was more completely retained than any mutated protein. Retained mutan ts had either a critical PreS stretch, or N-terminal myristate. Also, mutants of the latter class did not completely inhibit particulate bud ding, and could, in minor amounts, reach the Golgi, We conclude that ( i) the principal retention determinant can be traced to the same PreS segment in distinct strains and (ii) myristic acid does reinforce rete ntion in wild-type L, while acting in part as an HBsAg membrane anchor in mutants lacking the internal determinant.