PQ loop repeat
PF04193
Definition
Members of this family are all membrane bound proteins possessing a pair of repeats each spanning two transmembrane helices connected by a loop PMID:11731489. The PQ motif found on loop 2 is critical for the localisation of cystinosin to lysosomes PMID:11150305. However, the PQ motif appears not to be a general lysosome-targeting motif. It is thought likely to possess a more general function. Most probably this involves a glutamine residue PMID:11731489. Family members are membrane transporters since two members, cystinosin and PQLC2, transport cystine and cationic amino acids, respectively, across the lysosomal membrane PMID:11689434. The 2nd PQ-loop of cystinosin hosts the substrate-coupled H+ binding site underlying its H+ symport mechanism, suggesting that PQ-loop repeats have functional significance [[cite:PMID:22232659],[cite:PMID:23169667]]. It is thus likely that PQ-loop-containing proteins act as a family of membrane transporters. Some transport cystine and cationic amino acids, respectively, across the lysosomal membrane. Others transport lysine and or arginine across the lysosomal membrane in order to maintain the acidic homoeostasis PMID:22822152.
5 human proteins with this domain
Each is a reviewed human protein in the Seroatlas serome and a potential autoantibody target; this domain groups them into one antibody-relevant category. Every entry links to its own record.
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