MOLECULAR CHARACTERIZATION OF A GENOMIC REGION IN A LACTOCOCCUS BACTERIOPHAGE THAT IS INVOLVED IN ITS SENSITIVITY TO THE PHAGE DEFENSE-MECHANISM ABIA

Citation
Pk. Dinsmore et Tr. Klaenhammer, MOLECULAR CHARACTERIZATION OF A GENOMIC REGION IN A LACTOCOCCUS BACTERIOPHAGE THAT IS INVOLVED IN ITS SENSITIVITY TO THE PHAGE DEFENSE-MECHANISM ABIA, Journal of bacteriology, 179(9), 1997, pp. 2949-2957
Citations number
63
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
ISSN journal
0021-9193
Volume
179
Issue
9
Year of publication
1997
Pages
2949 - 2957
Database
ISI
SICI code
0021-9193(1997)179:9<2949:MCOAGR>2.0.ZU;2-1
Abstract
A spontaneous mutant of the lactococcal phage phi 31 that is insensiti ve to the phage defense mechanism AbiA was characterized in an effort to identify the phage factor(s) involved in sensitivity of phi 31 to A biA, A point mutation was localized in the genome of the AbiA-insensit ive phage (phi 31A) by heteroduplex analysis of a 9-kb region. The mut ation (G to T) was within a 738-bp open reading frame (ORF245) and res ulted in an arginine-to-leucine change in the predicted amino acid seq uence of the protein, The mutant phi 31A-ORF245 reduced the sensitivit y of phi 31 to AbiA when present in trans, indicating that the mutatio n in ORF245 is responsible for the AbiA insensitivity of phi 31A. Tran scription of ORF245 occurs early in the phage infection cycles of phi 31 and phi 31A and is unaffected by AbiA, Expansion of the phi 31 sequ ence revealed ORF169 (immediately upstream of ORF245) and ORF71 (which ends 84 bp upstream of ORF169). Two inverted repeats lie within the 8 4-bp region between ORF71 and ORF169, Sequence analysis of an independ ently isolated AbiA-insensitive phage, phi 31B, identified a mutation (G to A) in one of the inverted repeats, A 118-bp fragment from phi 31 , encompassing the 84-bp region between ORF71 and ORF169, eliminates A biA activity against phi 31 when present in trans, establishing a rela tionship between AbiA and this fragment, The study of this region of p hage phi 31 has identified an open reading frame (ORF245) and a 118-bp DNA fragment that interact with AbiA and are likely to be involved in the sensitivity of this phage to AbiA.