Biochemical modifications acetylation

Recent advances in mass spectrometry (MS) technology have provided researchers with an unparalleled ability to identify the types and patterns of secondary biochemical modifications found on proteins in living cells. Matrix-assisted laser desorption/ionization-MS (MALDI-MS) analyses have shown, for example, that HMGA proteins in vivo are simultaneously subject to complex patterns of phosphorylation, acetylation and methylation and that, within the same cell type, different isoforms of these proteins can exhibit quite different modification patterns [33]. Furthermore, these in vivo modifications have been demonstrated to markedly alter the binding affinity of HMGA proteins for both DNA and chromatin substrates in vitro [33]. Nevertheless, due to their number and complexity, it has been difficult to determine the actual biological function(s) played by these biochemical modifications in living cells. 

Shi Y, Lan L, Matson C, Mulhgan P, Whetstine JR, Cole PA, Casero RA, Shi Y (2004) Histone demethylation mediated by the nuclear amine oxidase homolog LSDl. Cell 119 941-953 Shilatifard A (2006) Chromatin Modifications by Methylation and Ubiquitination Implications in the Regulation of Gene Expression. Annu Rev Biochem 75 243-269 Sterner DE, Berger SL (2000) Acetylation of histones and transcription-related factors. Microbiol. Mol Biol Rev 64 435-459... 

The association between a histone tail modification and a particular functional state of chromatin, came with the demonstration that transcriptionally active chromatin fractions were enriched in acetylated histones, firstly by biochemical co-fractionationation ([8,9] and references therein) and then by Chromatin ImmunoPrecipitation, ChIP [10]. Subsequently, regions of transcriptionally silent constitutive and facultative heterochromatin, were shown, by immunofluorescence microscopy, to be under-acetylated [11,12]. This supported the idea that acetylation of the histone tails, with the associated loss of positive charge and reduction in DNA-binding constant, somehow caused chromatin to become more open (or less condensed ) and thereby more conducive to transcription. While this is likely to be an important contributory factor, it has now become clear that the... 

Ovalbumin, a member of the albumins. Ovalbumin is a glycoprotein (hen ovalbumin Mr 44.5 kDa 385 aa) characterized by four sites of post-translational modifications. Beside the acetylated N-terminus, the carbohydrate moiety is located at Asn , and the two phosphorylated serines at residues 68 and 344. Ovalbumin is a non-inhibitory member of the serine protease inhibitor family of the serpins. It has been classified as ovalbumin A1-A3, depending on the number of phosphorylated serine residues. Ovalbumin comprises 60% of the total protein amount of egg-white [A. D. Nisbet et al., Eur. J. Biochem. 1981, 115, 335 J. A. Huntington, P. E. Stein, J. Chromate. B 2001, 756, 189]. 

Alginate is a polymer composed of uronic acid monomers. While this acidic polysaccharide can be recovered from bacteria, the commercial source is brown seaweed. Both propylene glycol esterification and acetylation of the polymer cause an increase in the thickening capabilities of the gum. The acetylation of alginate by pseudomonal species demonstrates alternative biochemical methods for polysaccharide modification. 

It is quite striking that our current biochemical insight into the enzymatic reaction of histone tail acetylation, the causative agents of this modification (Section IV.C), and their involvement in transcriptional control in vivo is not paralleled by a similar understanding of the stmctural effects of histone tail hyperacetylation on chromatin, or of the mechanistic underpinnings of the general stimulatory effect that this modification has on the transcriptional machinery. 

As well as being involved in the oxidative consumption of fats it has been shown, predominantly by the work of Beevers and collaborators, that the jS-oxidation spiral participates in the biochemical reactions involved in the conversion of fats to sucrose during the germination of fatty seeds such as the castor bean. The mobilization of the fatty reserves involves hydrolysis and /3-oxidation as described above but the acetyl-CoA produced enters not the TCA cycle but a modification of it known as glyoxylate cycle (Fig. 4.10). In this cycle the... 

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