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Importance of BLV protease cleavage site residues P12-P9/P9'-P12' in binding to the PR substrate-grooves.

Posted by GaryLaco on 08 Sep 2022 at 17:07 GMT

There is an interesting result in this publication by Martin Flo and co-workers that I would like to focus more on. As noted in the first comment, and in the paper, when BLV PR was expressed as a fusion polyprotein with MBP (MBP-pr-BLV-PR) the BLV PR so rapidly cleaved itself out of the polyprotein at the N-and C-terminal cleavages site residues P12-P12’, that the soluble BLV PR underwent autoproteolysis resulting in no full length BLV PR accumulating in E. coli cell lysates.
In contrast, when Janos Motyan and coworkers expressed the BLV PR as a fusion polyprotein with MBP (MBP-linker-BLV-PR) they only included cleavage sites residues P8-P12’ for the BLV PR N-terminal site (1). And here is the interesting result, their MBP-linker-BLV-PR fusion polyprotein accumulated to high levels in inclusion bodies. This suggests that by removing residues P12-P9 from the N-terminal BLV PR cleavage site, the cleavage rate was slowed down enough to allow the MBP-linker-BLV-PR fusion polyprotein to accumulate in inclusion bodies. A similar expression strategy was used by Janos Motyan and coworkers to express HIV-1 and HTLV-1 PRs, and those PRs also accumulated in inclusion bodies as MBP-linker-PR fusion polyproteins (1). Together, the results by Martin Flo and coworkers and Janos Motyan and coworkers support the importance of retroviral cleavage site residues P12-9/P9’-P12’ in binding to the PR substrate-grooves, and in so doing enhancing PR cleavage rates in vivo and in vitro.

1) Motyan JA et. al, Different Mutation Tolerance of Lentiviral (HIV-1) and Deltaretroviral (BLV and HTLV) Protease Precursors, Viruses 2022, 14(9), 1888; https://doi.org/10.3390/v...

No competing interests declared.
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