THE HUMAN MYOSIN LIGHT-CHAIN KINASE (MLCK) FROM HIPPOCAMPUS - CLONING, SEQUENCING, EXPRESSION, AND LOCALIZATION TO 3QCEN-Q21

Myosin light chain kinase (MLCK), a key enzyme in muscle contraction, has been shown by immunohistol ogy to be present in neurons and glia. We describe here the cloning of the cDNA for human MLCK from hippocamp us, encoding a protein sequence 95% similar to smooth muscle MLCKs but less than 60% similar to skeletal muscle MLCKs. The cDNA clone detect ed two RNA transcripts in human frontal and entorhinal cortex, in hipp ocampus, and in jejunum, one corresponding to MLCK and the other proba bly to telokin, the carboxy-terminal 154 codons of MLCK expressed as a n independent protein in smooth muscle. Levels of expression were lowe r in brain compared to smooth muscle. We show that within the protein sequence, a motif of 28 or 24 residues is repeated five times, the sec ond repeat ending with the putative methionine start codon. These repe ats overlap with a second previously reported module of 12 residues re peated five times in the human sequence. In addition, the acidic C-ter minus of all MLCKs from both brain and smooth muscle resembles the C-t erminus of tubulins. The chromosomal localization of the gene for huma n MLCK is shown to be at 3qcen-q21, as determined by PCR and Southern blotting using two somatic cell hybrid panels. (C) 1995 Academic Press , Inc.