http://192.168.1.40:8080/xmlui/handle/123456789/1130 Sun, 31 May 2026 15:24:08 GMT 2026-05-31T15:24:08Z http://192.168.1.40:80/xmlui/bitstream/id/65188fc8-1b75-4112-aa53-39399393ade8/ajit.jpg http://192.168.1.40:8080/xmlui/handle/123456789/1130 http://192.168.1.40:8080/xmlui/handle/123456789/2439 Role of C-terminal residues in oligomerization and stability of lambda CII: Implications for lysis-lysogeny decision of the phage Datta, Ajit Bikram; Roy, S.; Parrack, P. A crucial element in the lysis-lysogeny decision of the temperate coliphage lambda is the phage protein CII, which has several interesting properties. It promotes lysogeny through activation of three phage promoters p(E), p(I) and p(aQ), recognizing a direct repeat sequence TTGCN(6)TTGC at each. The three-dimensional structure of CII, a homo-tetramer of 97 residue subunits, is unknown. It is an unstable protein in vivo, being rapidly degraded by the host protease HflB (FtsH). This instability is essential for the function of CII in the lysis-lysogeny switch. From NMR and limited proteolysis we show that about 15 C-terminal residues of CII are highly flexible, and may act as a target for proteolysis in vivo. From in vitro transcription, isothermal calorimetry and gel chromatography of CII (1-97) and its truncated fragments CIIA (4-81/82) and CIIB (4-69), we find that residues 70-81/82 are essential for (a) tetramer formation, (b) operator binding and (c) transcription activation. Presumably, tetramerization is necessary for the latter functions. Based on these results, we propose a model for CII structure, in which protein-protein contacts for dimer and tetramer formation are different. The implications of tetrameric organization, essential for CII activity, on the recognition of the direct repeat sequence is discussed. DOI: 10.1016/j.jmb.2004.09.098 Fri, 14 Jan 2005 00:00:00 GMT http://192.168.1.40:8080/xmlui/handle/123456789/2439 2005-01-14T00:00:00Z http://192.168.1.40:8080/xmlui/handle/123456789/1358 Escherichia coli HflK and HflC can individually inhibit the HflB (FtsH)-mediated proteolysis of lambda CII in vitro Bandyopadhyay, Kaustav; Parua, Pabitra Kumar; Datta, Ajit Bikram; Parrack, Pradeep lambda CII is the key protein that influences the lysis/lysogeny decision of by activating several phage promoters The effect of CII is modulated by a number of phage and host proteins including Escherichia colt HflK and HflC These membrane proteins copurify as a tightly bound complex 'HflKC' that inhibits the HfIB (FtsH)mediated proteolysis of CII both in vitro and in vivo Individual purification of HflK and HflC has not been possible so far, since each requires the presence of the other for proper folding. We report the first purification of HflK and HfIC separately as active and functional proteins and show that each can interact with HflB on its own and each inhibits the proteolysis of CII They also inhibit the proteolysis of E colt sigma(32) by HflB We show that at low concentrations each protein is dimeric, based on which we propose a scheme for the mutual interactions of HflB, HflC and HfIC in a supramolecular HflBKC protease complex (C) 2010 Elsevier Inc. All rights reserved DOI: 10.1016/j.abb.2010.06.030 Wed, 15 Sep 2010 00:00:00 GMT http://192.168.1.40:8080/xmlui/handle/123456789/1358 2010-09-15T00:00:00Z