Chromosomal mapping of genes encoding subunits of complex I from Neurospora crassa.
Fátima Ferreirinha, Teresa Almeida, Margarida Duarte and Arnaldo Videira - Instituto de
Biologia Molecular e Celular, Unidade Multidisciplinar de Investigação Biomédica and Instituto
de Ciências Biomédicas de Abel Salazar, University of Porto, Portugal.
The genes encoding the 21 kDa protein and the 19.3 kDa, 21.3 kDa and 24 kDa iron-sulfur
subunits of complex I were located, by RFLP analysis, in Linkage Groups IV, VI, VI and V,
respectively, of the Neurospora crassa genome.
Complex I or respiratory chain NADH dehydrogenase is located in the inner
mitochondrial membrane, where it catalyzes electron transfer from NADH to ubiquinone through
a series of protein-bound prosthetic groups, coupled to proton translocation across the membrane.
In mammals and N. crassa, seven subunits of this mitochondrial enzyme are encoded and
synthesized in the organelle, whereas about 30 others are imported from the cytoplasm. The
nuclear-coded genes are usually called nuo (for NADH:ubiquinone oxidoreductase) followed by
the molecular mass of the respective polypeptide. We have determined the chromosomal location
of four new nuclear genes encoding subunits of complex I by the analysis of segregation of
RFLPs among the strains of the multicent-2 cross kit (Metzenberg et al. 1984 Fungal Genet.
Newsl. 31:35-39). Using cDNAs encoding proteins of 19.3 kDa, 21 kDa, 21.3 kDa and 24 kDa as
probes (the homologues of bovine PSST, AQDQ, TYKY and 24 kDa proteins, respectively;
Azevedo et al. 1994 Biochim. Biophys. Acta 1188:159-161; Duarte et al. 1996 Biochim.
Biophys. Acta 1275:151-153; unpublished results), we have isolated the respective genomic
clones from a l J1 library obtained from the FGSC. Genomic DNA fragments containing the
genes were then labeled with different non-radioactive techniques employing either PCR or
random-primer labeling, and used in the RFLP analysis. The genes encoding the 21 kDa protein
and the 19.3 kDa, 21.3 kDa and 24 kDa iron-sulfur proteins were located in Linkage Groups IV,
VI, VI and V, respectively, of the N. crassa genome (Table 1). With these assignments, ten
nuclear-coded single-copy genes encoding subunits of complex I have been located (reviewed in
Videira 1998 Biochim. Biophys. Acta, in press).
Table 1. Segregation of RFLPs, related to complex I genes, among the strains of the multicent-2
cross kit
AABBCCDDEEEEFFGGHHIIJJKKLLMMNNOOPPQQRR
14671457135713145768141414582324142414
nuo19.3 M-MOMMMMOOMMMMOOOOOO-OOOMMOOOOMMMMOOMM
nuo21 MOMMMOOMMOOMOMOMOOOM-OOMOMOMMOM-OMMMMO
nuo21.3c M-OOMOOMOMOMOMMOOOMOOOOMOMOMOMMOMOMOOM
nuo24 M-O-MOOMOOMMMOOO-MOO-MMOOM-MOMOMMMOMM-