This family has an alpha/beta topology, with 13 conserved hydrophobic residues at its core and a putative active site containing a highly conserved cysteine [1]. Members of this family are involved in a range of physiological functions. The family in ...
This family has an alpha/beta topology, with 13 conserved hydrophobic residues at its core and a putative active site containing a highly conserved cysteine [1]. Members of this family are involved in a range of physiological functions. The family includes PaaJ (PhaH) Swiss:O84984 from Pseudomonas putida. PaaJ forms a complex with PaaG (PhaF) Swiss:O84982, PaaI (PhaG) Swiss:O84983 and PaaK (PhaI) Swiss:O84985, which hydroxylates phenylacetic acid to 2-hydroxyphenylacetic acid [2]. It also includes PaaD Swiss:P76080 from Escherichia coli, a member of a multicomponent oxygenase involved in phenylacetyl-CoA hydroxylation [3]. Furthermore, several members of this family are shown to be involved in iron-sulfur (FeS) cluster assembly. Iron-sulfur (FeS) clusters are inorganic co-factors that are are able to transfer electrons and act as catalysts [4]. They are involved in diverse cellular processes including cellular respiration, DNA replication and repair, antibiotic resistance, and dinitrogen fixation [5]. The biogenesis of such clusters from elemental iron and sulfur is an enzymatic process that requires a set of specialised proteins. Proteins containing this domain include the chloroplast protein HCF101 (high chlorophyll fluorescence 101), Swiss:Q6STH5, which has been described as an essential and specific factor for assembly of [4Fe-4S]-cluster-containing protein complexes such as the membrane complex Photosystem I (PSI) and the heterodimeric FTR (ferredoxin-thioredoxin reductase) complex [4] and is involved in the assembly of [4Fe-4S] clusters and their transfer to apoproteins [4]. The mature HCF101 protein contains this domain at the N-terminal as well as eight cysteine residues along the sequence. All cysteine residues are conserved among higher plants, but of the two cysteine residues located in this domain only Cys128 is highly conserved and is present in the highly conserved P-loop domain of the plant HCF101 (CKGGVGKS) [4]. SufT protein from Staphylococcus aureus is composed of this domain solely and is shown to be involved in the maturation of FeS proteins [5]. Given all this data, it is hypothesised that this domain might play a role in FeS cluster assembly.
