Site-specific mutagenesis has been used to prepare two mutant forms of the alpha subunit of tryptophan synthase from Salmonella typhimurium in which either cysteine-81 or cysteine-118 is replaced by a serine residue. These mutant proteins are potentially useful for x-ray crystallographic studies since a heavy metal binding site is specifically eliminated in each mutant. The purified mutant proteins are fully active in four reactions catalyzed by the wild type alpha 2 beta 2 complex of tryptophan synthase. However, the mutant alpha 2 beta 2 complexes dissociate more readily and are less heat-stable than the wild type alpha 2 beta 2 complex. Thus, cysteine-81 and cysteine-118 of the alpha subunit serve structural but not functional roles. Study holds ProTherm entries: 102, 103, 104 Extra Details: 2-mercaptoethanol (10 mM) and EDTA(1 mM) are added as additives. alpha subunit of tryptophan synthase; site-specific mutagenesis;,structural role; heavy metal binding site
Submitter: Connie Wang
Submission Date: April 24, 2018, 8:14 p.m.
|Number of data points||6|
|Proteins||Tryptophan synthase alpha chain ; Tryptophan synthase alpha chain|
|Assays/Quantities/Protocols||Experimental Assay: Tm ; Derived Quantity: dTm|
|Libraries||Mutations for sequence A:MERYENLFAQLNDRREGAFVPFVTLGDPGIEQSLKIIDTLIDAGADALELGVPFSDPLADGPTIQNANLRAFAAGVTPAQCFEMLALIREKHPTIPIGLLMYANLVFNNGIDAFYARCEQVGVDSVLVADVPVEESAPFRQAALRHNIAPIFICPPNADDDLLRQVASYGRGYTYLLSRSGVTGAENRGALPLHHLIEKLKEYHAAPALQGFGISSPEQVSAAVRAGAAGAISGSAIVKIIEKNLASPKQMLAELRSFVSAMKAASRA/B:TTLLNPYFGEFGGMYVPQILMPALNQLEEAFVRAQKDPEFQAQFADLLKNYAGRPTALTKCQNITAGTRTTLYLKREDLLHGGAHKTNQVLGQALLAKRMGKSEIIAETGAGQHGVASALASALLGLKCRIYMGAKDVERQSPNVFRMRLMGAEVIPVHSGSATLKDACNEALRDWSGSYETAHYMLGTAAGPHPYPTIVREFQRMIGEETKAQILDKEGRLPDAVIACVGGGSNAIGMFADFINDTSVGLIGVEPGGHGIETGEHGAPLKHGRVGIYFGMKAPMMQTADGQIEESYSISAGLDFPSVGPQHAYLNSIGRADYVSITDDEALEAFKTLCRHEGIIPALESSHALAHALKMMREQPEKEQLLVVNLSGRGDKDIFTVHDILKARGEI|