O'Shea Lab > People > Shawn Lo/title>  <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <SCRIPT SRC="../interact.txt"> </SCRIPT> <link rel="stylesheet" href="../eko_web.css"> </head> <body bgcolor="#FFFFFF" marginwidth="0" marginheight="0" leftmargin="0" topmargin="0" background="../img/i_bk.gif" text="#000000" link="#003366" vlink="#003366" alink="#cc9900" onLoad="load_images('internal'); return true"> <table width="575" border="0" cellspacing="0" cellpadding="0"> <tr> <td> <table width="575" border="0" cellspacing="0" cellpadding="0"> <tr> <td width="411" valign="bottom" align="left" bgcolor="#666666"><img src="../img/i_people_r02_c1.gif" width="411" height="62" alt="o'shea lab projects"></td> <td><img src="../img/i_people_r01_c7.gif" width="164" height="109" alt=""></td> </tr> </table> <table width="575" border="0" cellspacing="0" cellpadding="0"> <tr bgcolor="#CC3300"> <td width="90"><a href="../projects/index.html" onMouseOver = "red('on',1); return true" onMouseOut = "red('off',1); 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The autokinase/autophosphatase KaiC contains two autophosphorylation sites at S431 and T432, and that allows oscillation between four different KaiC phosphoforms over a 24-hour period. (2) This oscillation is controlled by interactions between KaiA, KaiB, and KaiC, and is thought to control rhythmic gene expression through downstream signaling. KaiA promotes the autophosphorylation of KaiC, while KaiB inhibits the activity of KaiA. (3) KaiC auto-dephosphorylates in the absence of KaiA. (4)<br> </p> <p>A defining feature of circadian clocks, including that of S. elongatus, is temperature compensation: the period of oscillation remains nearly constant over a broad range of physiologically relevant temperatures. Remarkably, the in vitro Kai protein oscillator is similarly temperature-compensated. In-vitro temperature compensation of KaiC phosphorylation was observed with period lengths of 22, 21 and 20 hrs at 25°C, 30°C, and 35°C, respectively. The system shows a [1]Q10 of 1.1 over this range as compared to a Q10 of between 2-3 typical of most biological systems. (1)<br> </p> <p>This research project aims to understand the mechanism by which the temperature compensation of the in vitro oscillator occurs. Two possible methods of temperature compensation are apparent. All individual phosphorylation and dephosphorylation rates could be compensated, or the rates could vary such that they would mutually offset one another.<br> </p> <p>Measurement would be taken of the rates of partial reactions at 25°C, 30°C and 35°C to isolate which rates and their corresponding interactions form the basis for temperature compensation. A mathematical model for the oscillator would be fitted to experimental data to isolate the rates of each individual phosphorylation and dephosphorylation reaction. Further work would proceed by hijacking the circadian cycles at critical points to observe the effect of temperature changes on well-understood protein interactions to propose a molecular basis for the compensation.</p> <p><br> </p> </td> </tr> </table> </td> <td width="1" bgcolor="#000000"><img src="../img/shim.gif" width="1" height="1"></td> </tr> <tr> <td width="1" bgcolor="#000000"><img src="../img/shim.gif" width="1" height="1"></td> <td width="411" bgcolor="#000000"><img src="../img/shim.gif" width="411" height="1"></td> <td width="1" bgcolor="#000000"><img src="../img/shim.gif" width="1" height="1"></td> </tr> </table> <p align="right"><a href="index.html">other people in the lab</a></p> <p> </p>  <p> </p> <p> </p> <p><a href="../projects/index.html">projects</a> :: <a href="index.html">people</a> :: <a href="../publications/index.html">publications</a> :: <a href="../affiliations/index.html">affiliations</a> :: <a href="../fun_stuff/index.html">fun stuff</a><br> <font color="#666666">--------------------------------------------------------------------------</font>--------<br> <a href="../contact/index.html">contact us</a> :: <a href="../extranet/index.html">lab extranet</a> ::<a href="../intranet/index.html"> lab intranet</a> :: <a href="../index.html"><font color="#CC3300">lab homepage</font></a></p> <p> </p> <p>Website questions, problems, or comments? <a href="mailto:falvo @ mcb. harvard. edu">Email the webmaster.</a><br> </p> </td> </tr> </table> </td> </tr> </table> </td> </tr> </table> </body> </html>