Simple modifications of the serpin reactive site loop convert SCCA2 into a cysteine proteinase inhibitor: A critical role for the P3 ' proline in facilitating RSL cleavage

Simple modifications of the serpin reactive site loop convert SCCA2 into a cysteine proteinase inhibitor: A critical role for the P3 ' proline in facilitating RSL cleavage

Author Luke, C. Google Scholar
Schick, C. Google Scholar
Tsu, C. Google Scholar
Whisstock, J. C. Google Scholar
Irving, J. A. Google Scholar
Bromme, D. Google Scholar
Juliano, L. Google Scholar
Shi, G. P. Google Scholar
Chapman, H. A. Google Scholar
Silverman, G. A. Google Scholar
Institution Childrens Hosp
Harvard Univ
Monash Univ
CUNY Mt Sinai Sch Med
Universidade Federal de São Paulo (UNIFESP)
Abstract The human squamous cell carcinoma antigens (SCCA) 1 and 2 are members of the serpin family that are 92% identical in their amino acid sequence. Despite this similarity, they inhibit distinct classes of proteinases. SCCA1 neutralizes the papain-like cysteine proteinases, cathepsins (cat) S, L, and K; and SCCA2 inhibits the chymotrypsin-like serine proteinases, catG and human mast cell chymase. SCCA2 also can inhibit catS, as well as other papain-like cysteine proteinases, albeit at a rate 50-fold less than that of SCCA1. Analysis of the mechanism of inhibition by SCCA1 revealed that the reactive site loop (RSL) is important for cysteine proteinase inhibition. the inhibition of catS by a mutant SCCA2 containing the RSL of SCCA1 is comparable to that of wild-type SCCA1. This finding suggested that there were no motifs outside and only eight residues within the RSL that were directing catS-specific inhibition. the purpose of this study was to determine which of these residues might account for the marked difference in the ability of SCCA 1 and SCCA2 to inhibit papain-like cysteine proteinases. SCCA2 molecules containing different RSL mutations showed that no single amino acid substitution could convert SCCA2 into a more potent cysteine proteinase inhibitor. Rather, different combinations of mutations led to incremental increases in catS inhibitory activity with residues in four positions (P1, P3', P4', and P11') accounting for 80% of the difference in activity between SCCA1 and SCCA2. Interestingly, the RSL cleavage site differed between wild-type SCCA2 and this mutant. Moreover, these data established the importance of a Pro residue in the P3' position for efficient inhibition of catS by both wild-type SCCA1 and mutated SCCA2. Molecular modeling studies suggested that this residue might facilitate positioning of the RSL within the active site of the cysteine proteinase.
Language English
Date 2000-06-20
Published in Biochemistry. Washington: Amer Chemical Soc, v. 39, n. 24, p. 7081-7091, 2000.
ISSN 0006-2960 (Sherpa/Romeo, impact factor)
Publisher Amer Chemical Soc
Extent 7081-7091
Origin http://dx.doi.org/10.1021/bi000050g
Access rights Closed access
Type Article
Web of Science ID WOS:000087778300006
URI http://repositorio.unifesp.br/handle/11600/26328

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