Aspartate Aminotransferase from an Alkalophilic Bacillus Contains an Additional 20-Amino Acid Extension at Its Functionally Important N-Terminus

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Abstract

Aspartate aminotransferase (AspAT), responsible for a minor part of the total AspAT enzymic activity in alkalophilic <i>Bacillus circulans</i>, was purified, its N-terminal amino acid sequence was determined, and its gene was cloned as two separate fragments. DNA sequencing showed an open reading frame of 432 amino acids (<i>M</i><sub>r</sub> 47, 439) exhibiting moderately low homology with AspATs from other sources. Sequence alignment of the enzyme with chicken mitochondrial, chicken cytoplasmic and <i>Escherichia coli</i> AspATs was performed with the MULTALIN program and further optimized assuming that the three-dimensional structures of the proteins were conserved. The primary structure of the studied AspAT diverged markedly from the others in the catalytically important small domain and in a segment of 31 amino acids in the large domain. The functional N-terminal arm was about two times longer than those of AspATs from other sources. According to the molecular model, the unique regions of <i>B. circulans</i> AspAT are all located together, forming a continuous network of contacts. Additional contacts formed by the elongated N-terminal arm may result in some limitation of domain movements in the alkalophilic enzyme in comparison to in other known AspATs.

Journal

  • The Journal of Biochemistry

    The Journal of Biochemistry 120(2), 425-432, 1996-08-01

    The Japanese Biochemical Society

References:  32

Codes

  • NII Article ID (NAID)
    10005189640
  • NII NACSIS-CAT ID (NCID)
    AA00694073
  • Text Lang
    ENG
  • Article Type
    ART
  • ISSN
    0021924X
  • Data Source
    CJP  J-STAGE 
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