Authors: Shailesh Sharma Gabriele Cavallaro Antonio Rosato
Publish Date: 2010/01/19
Volume: 15, Issue: 4, Pages: 559-571
Abstract
Multiheme ctype cytochromes MHCs are metalloproteins that can play various biochemical roles including enzymatic activity and electron transfer As electron transfer proteins the presence of multiple heme cofactors in the vicinity allows electrons to rapidly travel relatively long distances MHCs are often characterized by relatively low structural complexity with the heme cofactors being largely responsible for maintaining the structure in place owing to the protein–heme covalent linkages In this work we analyzed an extensive ensemble of 594 complete prokaryotic proteomes amounting to more than 19 million sequences to characterize their content in MHCs We identified 1659 MHCs in 258 organisms The presence of MHCs was found to correlate quite well with the capability of an organism to synthesize or take up heme For two organisms the presence of MHCs in the proteome could be taken as a hint to the presence of divergent heme uptake pathways The most common numbers of hemebinding motifs in a sequence were four 25 and two 23 followed by five 13 and ten 98 The average proteintoheme ratio was relatively similar for all MHCs except diheme proteins regardless of the number of motifs at around 60 ± 30 The latter ratio could in favorable cases be a useful indicator for functional assignments of novel MHCs Finally we showed that the amount of structural information currently available for MHCs is limited with respect to the diversity of this broad class of metalloproteins Experimental efforts in the structural investigation of MHCs are thus warranted
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