From owner-btk-mca@hgmp.mrc.ac.uk Tue Oct 9 04:10:46 2001 Return-Path: Received: from localhost (localhost [127.0.0.1]) by mercury.hgmp.mrc.ac.uk (Postfix) with ESMTP id E33D917A93 for ; Tue, 9 Oct 2001 04:10:45 +0100 (BST) Received: from localhost (localhost [127.0.0.1]) by mercury.hgmp.mrc.ac.uk (Postfix) with ESMTP id 93A9017A43 for ; Tue, 9 Oct 2001 04:10:43 +0100 (BST) Received: from niobium.hgmp.mrc.ac.uk (niobium [193.62.192.41]) by mercury.hgmp.mrc.ac.uk (Postfix) with ESMTP id 12B0A17A93 for ; Tue, 9 Oct 2001 04:10:35 +0100 (BST) Received: (from news@localhost) by niobium.hgmp.mrc.ac.uk (8.9.3+Sun/8.8.8) id EAA27164 for btk-mca-list@hgmp.mrc.ac.uk; Tue, 9 Oct 2001 04:07:24 +0100 (BST) X-Authentication-Warning: niobium.hgmp.mrc.ac.uk: news set sender to using -f From: pkuzmic@biokin.com (Petr Kuzmic) X-Newsgroups: bionet.metabolic-reg Subject: Re: delta-G of biochemical reactions Date: 8 Oct 2001 20:07:21 -0700 Organization: http://groups.google.com/ Lines: 35 Message-ID: <77754d4.0110081907.2c0d0376@posting.google.com> References: <3BB4AAA7.8790.DF1D392A@localhost> <77754d4.0110070742.6f61b8f@posting.google.com> <3BC0E343.192978FB@zonvark.wustl.edu> <77754d4.0110080604.47ee92d9@posting.google.com> <3BC1CAC8.1EFC4056@zonvark.wustl.edu> <3BC1F792.BE371B06@biokin.com> <3BC212B8.794A293F@zonvark.wustl.edu> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Complaints-To: groups-abuse@google.com To: btk-mca@hgmp.mrc.ac.uk Sender: owner-btk-mca@hgmp.mrc.ac.uk Precedence: bulk David Fell wrote: > > [...] the > way living systems keep away from equilibrium is by being open systems with > a flow of matter. I doubt there's a major flux of Zn or Cu through the > system, so what is the disequilibrium of these ions supposed to be coupled > to? It's not obvious to me that appeals to metal chaperones fit the bill here. Well, with a bit of tongue in cheek, one could say that this non-obvious nature and role of metal-trafficking proteins is the main reason why certain people are studying them [see also Science, 292, 2488 (2001)]. On a more serious note, I always thought that one does not have to have net flux of *particular* molecules or ions (such as Zn++) to observe a cell at disequilibrium with respect to those same chemical species. Couldn't it be that protein *turnover* inside the cell, in this case the synthesis of 'ZntR' and 'Zur' zinc trafficking proteins and their degradation by proteases, is keeping the cell at disequilibrium with respect to Zn++? It might be be interesting to see what is the half-life of these metal binding proteins. > Also, a small number of free atoms/ions is not by itself an argument for a > difficulty in attaining equilibrium, since it's the rate at which these are > exchanging with the bound sites that also counts [...]. Absolutely. This would be another expression of "kinetic control", wouldn't it? - Petr ------------------------------------------------------- P e t r K u z m i c, Ph. D. * BioKin Ltd. 1652 S. Grand Ave. * Suite 337 * Pullman, WA 99163 509.334.4131 * 509.332.3493 fax * http://www.biokin.com .