1tlf

From Proteopedia

Revision as of 06:59, 18 November 2007

UNPRECEDENTED QUATERNARY STRUCTURE OF E. COLI LAC REPRESSOR CORE TETRAMER: IMPLICATIONS FOR DNA LOOPING

Overview

The crystal structure of the tryptic core fragment of the lac repressor of, Escherichia coli (LacR) complexed with the inducer, isopropyl-beta-D-thiogalactoside was determined at 2.6 A resolution. The, quaternary structure consists of two dyad-symmetric dimers that are nearly, parallel to each other. This structure places all four DNA binding domains, of intact LacR on the same side of the tetramer, and results in a deep, V-shaped cleft between the two dimers. Each monomer contributes a, carboxyl-terminal helix to an antiparallel four-helix bundle that, functions as a tetramerization domain. Some of the side chains whose, mutation reduce DNA binding form clusters on a surface near the amino, terminus. Placing the structure of the DNA binding domain complexed with, operator previously determined by nuclear magnetic resonance onto this, surface results in two operators being adjacent and nearly parallel to, each other. Structural considerations suggest that the two dimers of LacR, may flexibly alter their relative orientation in order to bind to the, known varied spacings between two operators.

About this Structure

1TLF is a Single protein structure of sequence from Escherichia coli with EMC and IPT as ligands. The following page contains interesting information on the relation of 1TLF with [lac Repressor]. Full crystallographic information is available from OCA.

Reference

Crystal structure of lac repressor core tetramer and its implications for DNA looping., Friedman AM, Fischmann TO, Steitz TA, Science. 1995 Jun 23;268(5218):1721-7. PMID:7792597

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