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Characterization of N93S, I312T, and A333P missense mutations in two Japanese families with mitochondrial acetoacetyl‐CoA thiolase deficiency
Author(s) -
Fukao Toshiyuki,
Nakamura Haruki,
Song XiangQian,
Nakamura Kozue,
Orii Kenji E.,
Kohno Yoshinori,
Kano Masatsugu,
Yamaguchi Seiji,
Hashimoto Takashi,
Orii Tadao,
Kondo Naomi
Publication year - 1998
Publication title -
human mutation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 162
eISSN - 1098-1004
pISSN - 1059-7794
DOI - 10.1002/(sici)1098-1004(1998)12:4<245::aid-humu5>3.0.co;2-e
Subject(s) - biology , missense mutation , thiolase , genetics , mutation , gene , peroxisome
Abstract Mitochondrial acetoacetyl‐CoA thiolase (T2) deficiency is an inborn error of ketone body and isoleucine catabolisms. Japanese patients, GK01 and GK19, were found to be compound heterozygotes of 149delC and A333P, and N93S and I312T, respectively. The latter three missense mutations were individually characterized by analyses of transient expression of the cDNAs and heat stability. A333P and I312T subunits showed aberrant electrophoretic mobility on SDS‐PAGE. T2 protein was destabilized by A333P and existed as an insoluble form in the mitochondria. I312T mutation also destabilized T2 protein; however, some T2 protein was retained in soluble form and reduced residual activity was apparent. N93S mutation did not change the heat stability of T2 activity and the reduced residual activity was retained, however a considerable amount was observed in an insoluble form. The effects of mutations were interpreted based on a tertiary structural model of a subunit of the human T2. This model was constructed from the X‐ray crystal structure of the homologous peroxisomal 3‐ketoacyl‐CoA thiolase of Saccharomyces cerevisiae . On the basis of this model, the positions of Ala333 and Ile312 were far from the active site and the mutations would be expected to destabilize the tertiary structure of T2 subunit. By contrast, Asn93 is located near the active site and may function to maintain a local loop structure. The mutation of Asn93 could directly disrupt disposition of the active site. Hum Mutat 12:245–254, 1998. © 1998 Wiley‐Liss, Inc.