S. Kato et al., MOLECULAR-CLONING AND EXPRESSION OF MOUSE MG2-DEPENDENT PROTEIN PHOSPHATASE BETA-4 (TYPE 2C-BETA-4)(), Archives of biochemistry and biophysics, 318(2), 1995, pp. 387-393
A full-length complementary DNA (cDNA) clone (pTK-3) encoding an isofo
rm of Mg2+-dependent protein phosphatase beta (MPP beta-4) was isolate
d for the first time from a mouse melanocyte cDNA library. It was stro
ngly suggested that the mRNA corresponding to the pTK-3 insert was a s
plicing variant of a single pre-mRNA that also encodes MPP beta-1 and
-2 (T. Terasawa, T. Kobayashi, T. Murakami, M. Ohnishi, S. Kato, O. Ta
naka, H. Kondo, H. Yamamoto, T. Takeuchi, and S. Tamura, 1993, Arch, B
iochem. Biophys, 307, 342-349). The amino acid sequence of MPP beta-4
differed from those of MPP beta-1 and -2 only at the carboxyl terminal
region. Analysis by reverse transcriptase polymerase chain reaction (
RT-PCR) revealed that MPP beta-4 mRNA was expressed only in testis and
intestine and not in other mouse tissues tested. Specific expression
of the mRNA signals of two other isoforms of MPP beta, MPP beta-3 and
-5 (a novel isoform), in testis and intestine was also demonstrated by
the RT-PCR. The carboxyl terminal region of MPP beta-5 was found to h
ave a chimera structure composed of part of MPP beta-1 and part of MPP
beta-3. The recombinant MPP beta-3 and -4 and the putative MPP beta-5
expressed in Escherichia coli cells exhibited Mg2+-dependent and okad
aic acid-insensitive protein phosphatase activities. It was demonstrat
ed that the mRNA expression levels of MPP beta-3, -4, and -5 alter acc
ording to the maturation of mouse testis. These resuits suggest that t
he complex structure of MPP beta isoforms and their tissue- and develo
pmental stage-specific expression reflect the variety of their physiol
ogical functions. (C) 1995 Academic Press, Inc.