tag:blogger.com,1999:blog-37148773.post4140101323232820178..comments2024-03-27T14:50:47.345-04:00Comments on <center>Sandwalk</center>: Protein TurnoverLarry Moranhttp://www.blogger.com/profile/05756598746605455848noreply@blogger.comBlogger5125tag:blogger.com,1999:blog-37148773.post-76888671601521018992008-06-14T18:42:00.000-04:002008-06-14T18:42:00.000-04:00It should also be noted that proteosomal degradati...It should also be noted that proteosomal degradation requires that proteins to be degraded generally be poly-ubiquitinated, whereas mono-ubiquitination is used for signaling, activity modulation and subcellular localization etc. The specific lysine to which the (poly)ubiquitination is conjugated also makes a very large difference in subsequent downstream protein processing.Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-37148773.post-7412993126235974912008-06-13T20:17:00.000-04:002008-06-13T20:17:00.000-04:00What is the rate of protein turnover in (g/aa day)...What is the rate of protein turnover in (g/aa day)if breakdown is greater than synthesis, is it the difference of the two? or is it equal to synthesis? anyone?PhD Studenthttps://www.blogger.com/profile/18400649844608283066noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-36756435972657371542007-06-13T17:43:00.000-04:002007-06-13T17:43:00.000-04:00I doubt proteasomes could ever act in reverse. The...<EM>I doubt proteasomes could ever act in reverse. </EM><BR/><BR/>There are a number of papers demonstrating that proteasomes can in fact act in reverse; it seems to be, unsurprisingly, a rare event, but detectable in the context of MHC class I antigen presentation. See, for example, <BR/>Science. 2006 Sep 8;313(5792):1444-7. <BR/>and <BR/>Science. 2004 Apr 23;304(5670):587-90.iayorkhttps://www.blogger.com/profile/10717810444752993915noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-43156115267589772362007-06-07T02:11:00.000-04:002007-06-07T02:11:00.000-04:00I doubt proteasomes could ever act in reverse. Th...I doubt proteasomes could ever act in reverse. The peptide hydrolysis is achieved via nucleophilic attack. And dehydrating the proteasome would change it's structure and probably eliminate any catalytic activity.<BR/><BR/>However, theoretically it's possible that changing the structure (via dehydration) would result in a new active site that could <I>form</I> peptide bonds instead of <I>break</I> them, but that would be a coincidence for the record books...Ryanhttps://www.blogger.com/profile/09229048051639753761noreply@blogger.comtag:blogger.com,1999:blog-37148773.post-6892087924008970762007-06-05T23:58:00.000-04:002007-06-05T23:58:00.000-04:00Proteases only hydrolyze peptides when the equilib...Proteases only hydrolyze peptides when the equilibrium favors it. Under conditions of dehydration, the equilibrium favors the making of peptides. <BR/><BR/>As the lysosome shrinks, does it ever get sufficiently dehydrated that proteases might run in the other direction and make peptides out of amino acids? The lysosome is highly enriched with cysteine, and cysteine proteases. <BR/><BR/>Might this be a way that proteases could "self-assemble" and select for activity via diurnal cycles of hydration and dehydration in a pre-biotic Earth?daedalus2uhttps://www.blogger.com/profile/10416564922288784455noreply@blogger.com