Utilization of a calmodulin lysine methyltransferase co-expression system for the generation of a combinatorial library of post-translationally modified proteins

Roberta Magnani, Brian Chaffin, Emerson Dick, Michael L. Bricken, Robert L. Houtz, Luke H. Bradley

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


By successfully incorporating sequence diversity into proteins, combinatorial libraries have been a staple technology used in protein engineering, directed evolution, and synthetic biology for generating proteins with novel specificities and activities. However, these approaches mostly overlook the incorporations of post-translational modifications, which nature extensively uses for modulating protein activities in vivo. As an initial step of incorporating post-translational modifications into combinatorial libraries, we present a bacterial co-expression system, utilizing a recently characterized calmodulin methyltransferase (CaM KMT), to trimethylate a combinatorial library of the calmodulin central linker region. We show that this system is robust, with the successful over-expression and post-translational modification performed in Escherichia coli. Furthermore we show that trimethylation differentially affected the conformational dynamics of the protein upon the binding of calcium, and the thermal stability of the apoprotein. Collectively, these data support that when applied to an appropriately designed protein library scaffold, CaM KMT is able to produce a post-translationally modified library of protein sequences, thus providing a powerful tool for future protein library designs and constructions.

Original languageEnglish
Pages (from-to)83-88
Number of pages6
JournalProtein Expression and Purification
Issue number2
StatePublished - Dec 2012

Bibliographical note

Funding Information:
BC conducted research as part of his Georgetown College Honors Thesis Project and was supported by a summer undergraduate research fellowship from the Howard Hughes Medical Institute program (GCPALS). ED conducted research as part of his Agriculture Biotechnology (ABT 395) undergraduate research project. MLB conducted research as part of his University of Kentucky Honors Thesis project. MLB and ED were supported in part by summer fellowships from the University of Kentucky Office of Undergraduate Research. Other support was obtained partially from a pilot project Grant from the NIH National Center for Research Resources (NCRR) Grant P20 RR020171 (LHB), the Kentucky Science and Engineering Foundation (Grant Agreement # KSEF-148-502-207-201 with the Kentucky Science and Technology Corporation) (LHB), and the University of Kentucky College of Medicine Startup funds (LHB).


  • High-quality libraries
  • Post-translational modification
  • Protein library design
  • Synthetic biology

ASJC Scopus subject areas

  • Biotechnology


Dive into the research topics of 'Utilization of a calmodulin lysine methyltransferase co-expression system for the generation of a combinatorial library of post-translationally modified proteins'. Together they form a unique fingerprint.

Cite this