Carbohydrate kinase domain containing protein (abbreviated as CARKD), encoded by CARKD gene, is a human protein of unknown function. The CARKD gene encodes proteins with a predicted mitochondrial propeptide (mCARKD), a signal peptide (spCARKD) or neither of them (cCARKD). Confocal microscopy analysis of transfected CHO (Chinese-hamster ovary) cells indicated that cCARKD remains in the cytosol, whereas mCARKD and spCARKD are targeted to the mitochondria and the endoplasmic reticulum respectively.[6] The protein is conserved throughout many species, and has predicted orthologs through eukaryotes, bacteria, and archea.
CARKD appears to be ubiquitously expressed at high levels. Expression data in the human protein, and the mouse ortholog, indicate its expression in almost all tissues.[13][14] One peculiar expression pattern of CARKD is its differential expression through the development of oligodendrocytes. Its expression is lower in oligodendrocyte progenitor cells than in mature oligodendrocytes.[15]
The human protein apolipoprotein A-1 binding precursor (APOA1BP) was predicted to be a binding partner for CARKD.[16] This prediction is based on co-occurrence across genomes and co-expression. In addition to these data, the orthologs of CARKD in E. coli contain a domain similar to APOA1BP. This indicates that the two proteins are likely to have originated from a common evolutionary ancestor and, according to Rosetta stone analysis theory,[17] are likely interaction partners even in species such as humans where the two proteins are not produced as a single polypeptide.
^Marbaix AY, Tyteca D, Niehaus TD, Hanson AD, Linster CL, Van Schaftingen E (15 May 2014). "Occurrence and subcellular distribution of the NADPHX repair system in mammals". The Biochemical Journal. 460 (1): 49–58. doi:10.1042/bj20131482. PMID24611804.
