Identification of binding sites on the regulatory A subunit of protein phosphatase 2A for the catalytic C subunit and for tumor antigens of simian virus 40 and polyomavirus.

Protein phosphatase 2A is composed of three subunits: the catalytic subunit C and two regulatory subunits, A and B. The A subunit consists of 15 nonidentical repeats and has a rodlike shape. It is associated with the B and C subunits as well as with the simian virus 40 small T, polyomavirus small T, and polyomavirus medium T tumor antigens. We determined the binding sites on subunit A for subunit C and tumor antigens by site-directed mutagenesis of A. Twenty-four N- and C-terminal truncations and internal deletions of A were assayed by coimmunoprecipitation for their ability to bind C and tumor antigens. It was found that C binds to repeats 11 to 15 at the C terminus of A, whereas T antigens bind to overlapping but distinct regions of the N terminus. Simian virus 40 small T binds to repeats 3 to 6, and polyomavirus small T and medium T bind to repeats 2 to 8. The data suggest cooperativity between C and T antigens in binding to A. This is most apparent for medium T antigen, which can only bind to those A subunit molecules that provide the entire binding region for the C subunit. We infer from our results that B also binds to N-terminal repeats. A model of the small T/medium T/B-A-C complexes is presented.

Roeckel, D (författare)
Fait, J (författare)
Bergqvist, AndersUppsala universitet,Institutionen för medicinska vetenskaper,Institutionen för medicinsk biokemi och mikrobiologi(Swepub:uu)abe14202 (författare)
Magnusson, G (författare)
Walter, G (författare)
Uppsala universitetInstitutionen för medicinska vetenskaper (creator_code:org_t)

Av författaren/redakt...: Ruediger, R; Roeckel, D; Fait, J; Bergqvist, Ander ...; Magnusson, G; Walter, G

Om ämnet

MEDICIN OCH HÄLSOVETENSKAP: MEDICIN OCH HÄLS ...; och Medicinska och f ...; och Mikrobiologi ino ...

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