期刊
JOURNAL OF BIOLOGICAL CHEMISTRY
卷 278, 期 18, 页码 15917-15921出版社
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M301643200
关键词
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Ssu72 is an essential and highly conserved protein involved in mRNA transcription and X-end processing. The biochemical function of Ssu72 was so far unknown. We report here evidence that Ssu72 is a phosphatase that resembles protein tyrosine phosphatases (PTPases). First, recombinant Ssu72 cleaves the phosphotyrosine analogue p-nitrophenylphosphate, and this catalytic activity is impaired by PTPase-inhibiting agents. Second, the Ssu72 sequence contains the CX5R signature motif of PTPases; mutation of the catalytic cysteine in this motif abolishes Ssu72 activity in vitro and has been shown to confer lethality in vivo. Third, secondary structure prediction and site-directed mu-tagenesis predict that Ssu72 adopts the fold of PTPases of the low molecular weight family. Distinguishing features, such as a short aspartate loop at the active site, suggest however that Ssu72 is the founding member of a new phosphatase subfamily. The novel Ssu72 activity may regulate coupling events during mRNA biogenesis.
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