Functional Analysis of the Superfamily 1 DNA Helicases Encoded by Mycoplasma pneumoniae and Mycoplasma genitaliumReportar como inadecuado

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The DNA recombination and repair machinery of Mycoplasma pneumoniae is composed of a limited set of approximately 11 proteins. Two of these proteins were predicted to be encoded by neighboring open reading frames ORFs MPN340 and MPN341. Both ORFs were found to have sequence similarity with genes that encode proteins belonging to the DNA helicase superfamily 1 SF1. Interestingly, while a homolog of the MPN341 ORF is present in the genome of Mycoplasma genitalium ORF MG244, MPN340 is an M. pneumoniae-specific ORF that is not found in other mycoplasmas. Moreover, the length of MPN340 1590 base pairs bp is considerably shorter than that of MPN341 2148 bp. Examination of the MPN340-encoded amino acid sequence indicated that it may lack a so-called 2B subdomain, which is found in most SF1 DNA helicases. Also, the MPN340-encoded amino acid sequence was found to differ between subtype 1 strain M129 and subtype 2 strain FH at three amino acid positions. Both protein variants, which were termed PcrAsM129 and PcrAsFH, respectively, as well as the MPN341- and MG244-encoded proteins PcrAMpn and PcrAMge, respectively, were purified, and tested for their ability to interact with DNA. While PcrAMpn and PcrAMge were found to bind preferentially to single-stranded DNA, both PcrAsM129 and PcrAsFH did not demonstrate significant DNA binding. However, all four proteins were found to have divalent cation- and ATP-dependent DNA helicase activity. The proteins displayed highest activity on partially double-stranded DNA substrates carrying 3′ single-stranded extensions.

Autor: Silvia Estevão, Helga U. van der Heul, Marcel Sluijter, Theo Hoogenboezem, Nico G. Hartwig, Annemarie M. C. van Rossum, Cornelis



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