Molecular cloning of a chicken lung cDNA encoding a novel protein kinase with N-terminal two LIM/double zinc finger motifs
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Identification of Functional Protein Regions Through Chimeric Protein Construction
Published on: January 8, 2019
K Ohashi1, J Toshima, K Tajinda
1Department of Biology, Faculty of Science, Kyushu University, Fukuoka.
Abstract:
Using the cDNA fragment of chicken c-sea receptor tyrosine kinase as a probe, we isolated from a chicken lung cDNA library overlapping cDNA clones encoding a novel protein kinase, which we termed LIM-kinase (LIMK). The predicted polypeptide of 642 amino acid residues contains remarkable structural features, composed of the N-terminal two tandemly arrayed LIM/double zinc finger motifs and the C-terminal unusual protein kinase domain. To our knowledge, a protein kinase containing the LIM motif in the molecule has not heretofore been described. The protein kinase domain of LIMK shares highly conserved residues with the known protein kinases, but LIMK is unique in that it contains the sequence DLNSHN in subdomain VIB and a short, highly basic insert sequence, which may function as a signal for nuclear localization, between subdomain VII and VIII in the protein kinase domain. Northern blot analysis revealed that the single species of LIMK mRNA of 3.8 kb is expressed predominantly in the lung, and faintly in the kidney, liver, brain, spleen, gizzard, and intestine. As the LIM motif is thought to be involved in protein-protein interactions by binding to another LIM motif, and is often present in the homeodomain-containing proteins involved in cell fate determination and in the oncogenic nuclear proteins (rhombotins), it is likely that LIMK is involved in developmental or oncogenic processes through interactions with these LIM-containing proteins.
Insights
Researchers discovered a novel protein kinase, LIM-kinase (LIMK), in chickens. This kinase contains unique LIM/double zinc finger motifs and a distinct protein kinase domain, suggesting roles in cell development and cancer.
Area of Science:
- Molecular Biology
- Biochemistry
- Cell Biology
Background:
- The c-sea receptor tyrosine kinase is a known protein involved in cellular signaling.
- Protein kinases play crucial roles in cellular regulation and signaling pathways.
- The LIM motif is recognized for its role in protein-protein interactions and is found in various regulatory proteins.
Purpose of the Study:
- To identify and characterize novel protein kinases.
- To investigate the structural and functional properties of a newly discovered kinase.
Main Methods:
- Isolation of cDNA clones from a chicken lung cDNA library using a c-sea receptor tyrosine kinase probe.
- Sequence analysis to determine the polypeptide structure of the novel protein kinase.
- Northern blot analysis to assess gene expression patterns.
Main Results:
- Identification of a novel protein kinase, termed LIM-kinase (LIMK), with a unique structure including N-terminal LIM/double zinc finger motifs and an unusual protein kinase domain.
- LIMK exhibits conserved residues typical of protein kinases but possesses unique sequences, including a potential nuclear localization signal.
- LIMK mRNA is predominantly expressed in the lung, with lower levels in other tissues like the kidney, liver, and brain.
Conclusions:
- LIM-kinase represents a novel class of protein kinases containing LIM motifs.
- The unique structural features of LIMK suggest potential involvement in protein-protein interactions and cellular processes.
- Given the known functions of LIM motifs in developmental and oncogenic proteins, LIMK may play a role in cell fate determination or cancer development.
