THE BRADYRHIZOBIUM-JAPONICUM SEROCLUSTER-123 HYPERREITERATED DNA REGION, HRS1, HAS DNA AND AMINO-ACID-SEQUENCE HOMOLOGY TO IS1380, AN INSERTION-SEQUENCE FROM ACETOBACTER-PASTEURIANUS

We have sequenced and analyzed the hyperreiterated DNA region, HRS1, f rom Bradyrhizobium japonicum USDA 424. The 2.1-kb HRS1 fragment is clo sely linked to the B. japonicum common and genotype-specific nodulatio n genes in serogroup 123 and 127 strains. Southern hybridization analy ses indicated that one copy of HRS1 is also located next to the fixRni fA locus in B. japonicum USDA 424. Nucleotide sequence analysis reveal ed the presence of a 4-bp target site duplication in HRS1 which is ide ntical to a terminal repeat found in the B. japonicum USDA 110 repeate d sequence RSalpha. Computer searches of the PIR (Protein Identificati on Resource) protein data base revealed a high degree of amino acid se quence homology between a putative 329-amino-acid polypeptide from HRS 1 and a large polypeptide from IS1380, an insertion sequence from Acet obacter pasteurianus. RNA slot blot hybridizations suggest that transc ripts showing homology to HRS1 are constitutively produced in strains USDA 424 (serogroup 127) and USDA 438 (serogroup 123).