First, it really consists of a "part" called TradePriceRequest. What's this? Defined in the schema:
<element name="TradePriceRequest">
   <complexType>
     <all>
       <element name="tickerSymbol" type="string"/>
     </all>
   </complexType>
</element>
<element name="TradePrice">
   <complexType>
     <all>
       <element name="price" type="float"/>
      </all>
   </complexType>
</element>